Showing papers on "Atmospheric pressure published in 1984"

Measurement of anode falls and anode heat transfer in atmospheric pressure high intensity arcs

Abstract: Electric probe measurements have been performed at and close to a plane, water‐cooled anode surface in atmospheric pressure, high intensity argon arcs for different arc configurations which in turn, result in two distinctly different anode arc roots (diffuse and constricted) An adjustable fine wire probe penetrating through a small hole in the center of a flat anode allows for potential and electron temperature measurements in the anode boundary layer For the parameter range covered by this investigation (100 A≤I≤250 A) the results reveal negative anode falls ranging from approximately −21 to −14 V Electron temperatures at the anode surface range from 8800 to 9800 K Calorimetric energy balances from which the contributions of the various modes of heat transfer to the anode may be derived, indicate the importance of convective heat transfer to the anode The results of the calorimetric studies as well as of the anode fall measurements are consistent with a revised anode heat transfer model which take

Method and apparatus for the mass spectrometric analysis of solutions

Abstract: An electrospray ion source for a mass spectrometer capable of generating ions from samples dissolved in a solution comprises a capillary tube (30) through which the said solution is pumped into a first chamber maintained substantially at atmospheric pressure and in which an inert gas, preferably heated, is flowing in a direction counter to the flow of the solution, and a small orifice (4) in the end wall (1) of the chamber opposite to and aligned with the capillary. A high potential difference is applied between the capillary tube (30) and the end wall (1) so thatthe solution is electrosprayed into the chamber and ions characteristic of the sample are formed. These ions are desolvated to a controllable extent by the inert gas, which is usually heated to improve the efficiency of the process and increase the maximum permissible flow rate of solution. The ions so formed pass through the small orifice (4) into a second chamber maintained at a reduced pressure, and into a mass spectrometer (29). Alternatively an additional pressure reduction stage can be included, so that the ions pass into a third chamber maintained at a still lower pressure in which the mass spectrometer (29) is situated through a hole (23) in skimmer (24). The ion source is particularly effective for the production of unfragmented and unsolvated ions from thermally unstable or involatile samples, and may be used as a liquid chromatograph - mass spectrometer interface.

Microwave absorption and plasma heating due to microwave breakdown in the atmosphere

Abstract: The propagation and absorption of microwaves above the breakdown threshold in the atmosphere with the self‐consistent breakdown plasma are investigated. Typical hydrodynamic calculations show that an ionization front is rapidly formed which moves toward the microwave source and consequently decouples the microwaves from the original ionization region. By focusing the microwaves or using a reflector, ionization can be confined to localized regions where the microwave strength is high enough to cause breakdown even though the incoming microwaves are below threshold. In a strongly collisional atmosphere, it is found that the cutoff plasma density, which roughly equals the collisionless cutoff density multiplied by the collisionality, is much higher than the calculated maximum density. This results in high absorption that increases with microwave power, decreases with atmospheric pressure, and is quite independent of other parameters. In a weakly collisional atmosphere, breakdown easily creates a plasma density higher than the cutoff density and causes reflection. It is found that the reflection decreases with the collisionality of the system and is quite independent of the microwave strength. In general, the microwave field strength in the ionization regions is attenuated to the breakdown value at steady state, and the resulting electron temperature is about 2 eV, independent of the incident microwave flux. Limitations of the calculations are due to the availability of experimental data for the rate coefficients, but comparison to results from recent focused microwave experiments shows excellent agreement.

High temperature and pressure preparation and properties of iron carbides Fe7C3 and Fe3C

Abstract: The formation regions of Fe7C3 and Fe3C were determined at high temperature and high pressure in the iron-graphite system. Fe7C3 formed at relatively higher pressures and Fe3C at lower pressures. Both Fe7C3 and Fe3C were isolated from coexisting excess carbon powders by a magnetic method. Fe7C3 had a Curie point of 250° C and a saturation magnetization of 120 emu g−1 at room temperature and Fe3C had those of 210° C and 125 emu g−1. Fe7C3 decomposed to Fe3C and carbon at 600° C, but to α-Fe and carbon at 700° C at atmospheric pressure, and Fe3C to α-Fe and carbon at 700° C. The substitution of other metals (Cr, Mo and W) for iron in these carbides leads to changes in the thermal stabilities and the magnetic properties.

A mathematical model for

Abstract: A mathematical model for decompression is presented. It includes a first-order linear differential equation, which models the diffusion of gases within the body, as well as initial conditions and a nonlinear constraint inequality which insures safety from decom- pression sickness. The model is solved (numerically and/or analytically) under various hypotheses, and the results are compared with the U.S. Navy Dive Table. which changes in pressure on the body may result in a buildup of air bubbles in the tissues. This condition is known as decompression sickness or, more commonly, the "bends." Scuba diving is a popular sport in which participants subject themselves to changes in pressure. Other examples are provided by the man-in-space program and certain tunnelling operations in which air pressure on the body is alternately increased and decreased. During respiration, air is inspired into the lungs, from which it enters the blood. The air in solution in the blood is then carried to the body tissues where it is released by the blood into the tissues. The driving force for the exchange of gas at either the lungs or the body tissues is the difference in the partial pressures of the different gases on either side of the transaction site. In the normal situation in which the pressure on the body is decreased, the pressure of the air that is breathed is less than that in solution in the body tissues. When this happens, the body will act to relieve the difference in pressure. The blood will pick up excess gas in solution in the tissues and transfer it to the lungs from which it is exhaled. A dangerous situation occurs when the outside pressure is decreased so much that the tissue-blood-lung transfer of excess gas cannot take place rapidly enough. In this case, the gas pressure in the tissues will force the excess gas out of solution, resulting in the formation of gas bubbles in the tissues. The diffusion of a gas between lungs and blood and between blood and tissues can be modeled mathematically. Henry's Law is a linearized pressure law which guarantees that a gas will flow from a higher pressure region to a lower pressure region at a rate which is proportional to the difference in the partial pressure of the gas in the two different regions. In what follows, we shall be concerned mainly with the effect of nitrogen and carbon

Parametric study of the flow and temperature fields in an inductively coupled r.f. plasma torch

Abstract: A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate, input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement tube, are considerably altered by the changes in the torch operating conditions.

Polarization of laser-induced fluorescence in OH in an atmospheric pressure flame

Abstract: Measurements have been made of the polarization of the laser-induced fluorescence in OH in the burnt gases of a CH4/O2 flame diluted with N2, Ar, or He. A significant degree of polarization is observed for the lines emitted by the pumped level. Although elastic depolarizing collisions occur, they must compete with rapid quenching, resulting in a freezing of the coherence generated by the polarized laser. The variation of apparent line strength ratios with pump line and J is in agreement with theoretical expectations. The coherence is preserved to a small degree following collisional transfer to nearby rotational levels. The implications concerning relative collision rates and for flame diagnostic measurements are discussed.

Effects of metallic vapor on the properties of an argon arc plasma

Abstract: During thermal plasma processing of materials, vapor generated from injected particulate matter will enter the plasma. Even traces of metallic vapors may have a strong effect on the properties and the behavior of the plasma and on the associated heat flux to the injected particles. In this paper a model system is considered in which an argon plasma at atmospheric pressure is “contaminated” by small amounts of copper vapor. By using the Chapman-Enskog approximation for a multicomponent gas mixture the transport properties are calculated for such a contaminated argon plasma. The results show that there is a drastic effect on the electrical properties. For temperatures below 104 K, the electrical conductivity, for example, increases by more than an order of magnitude if metallic vapor is present. The presence of metallic contaminants is also somewhat felt by the reactional thermal conductivity. In contrast, there is no effect on the heavy-particle properties as long as the percentage of the contaminants remains small.

Portable instrument to test pressure/flow of ventricular shunt valves

Abstract: A portable instrument system is provided for the testing of pressure and flow characteristics of implantable ventricular shunt valves using a gaseous testing fluid that may be drawn from the testing environment. The system includes a rate pump having a control mechanism that provides a variety of selective constant flow rates so that the valve characteristics can be determined under various operating conditions. Fluid communication is provided between the pump, the valve and a pressure sensing device such that the pressure sensing device receives the same pressure and flow rate that the valve does. Typically, the pressure sensing device is a gauge transducer that utilizes atmospheric pressure as a reference point and senses the changes in the gas pressure in the valve, relaying the pressure readings to a digital display or chart recorder.

Catalytic reactions of hydrocarbon with carbon dioxide over metallic catalysts

Abstract: The catalytic reaction between hydrocarbons and carbon dioxide, e.g. CH4+ +CO2→2CO+2H2 and C6H6CH3+CO2→C6H6+2CO+H2, has been investigated over various metallic catalysts under atmospheric pressure. In general, Rh−Al2O3 catalyst was found to be excellent in activity and selectivity. The reaction rates were moderately dependent on the pressure of carbon dioxide, whereas it was little influenced by the pressure of hydrocarbon.

Nonisostatic Response of Sea Level to Atmospheric Pressure in the Eastern Mediterranean

Abstract: We analyze 5 months of sea-level data from Katakolon, Greece, in terms of local atmospheric pressure and the two components of geostrophic wind. The response to pressure is isostatic at low and high frequencies, but significantly nonisostatic for intermediate frequencies centered on about 0.01 cycles per hour. The response is consistent with a simple theory in which the fluctuating barotropic flow through the Straits of Gibraltar and Sicily is geostrophically controlled at low frequency. The local geostrophic wind contributes very little to the sea level variance; the response coefficients, while not well determined, are qualitatively as expected and quantitatively correspond to a very narrow near-shore region of shallow water.

Three-photon-excited fluorescence detection of atomic hydrogen in an atmospheric-pressure flame

Abstract: By using three-photon excitation at 291.7 nm of the n = 4 hydrogen level and observing Balmer-beta radiation at 486.1 nm, hydrogen atoms in an atmospheric C(2)H(2)/O(2) flame have been detected. Other schemes for hydrogen detection were also tried, and the results are discussed.

On the absence of shear mode softening in single-crystal fayalite Fe 2 SiO 4 at high pressure and room temperature

Abstract: The geophysical importance of the kinetics of the olivine → spinel phase transformation has stimulated considerable interest in the transformation mechanism. Both nucleation-and-growth and diffusionless martensitic models have been proposed. It has recently been suggested that a martensitic transformation (effected by partial dislocations associated with the (100) [001] slip system) would probably be accompanied by premonitory pressure-induced softening of the shear moduli c 55 and c 66. We have explored this possibility by measurement of the modulus c 55 for a single crystal of fayalite over a pressure range of 3 GPa (at 295 K) by ultrasonic interferometry. The variation of c 55 with pressure is described by a quadratic with the parameters (c 55)0=46.90±0.04 GPa, (∂c 55/∂P)0=1.715±0.004 and (∂2 c 55/∂P 2)0=−(0.136±0.003) GPa−1 where the subscript ‘0’ refers to atmospheric pressure and 295 K. The first pressure derivative is comparable with those for forsterite and ∼Fo90 olivine in spite of the much greater proximity of fayalite to the olivine⇌spinel phase boundary. The absence of pronounced pressure-induced shear mode softening in this study, along with similar results from a recent ultrasonic study of polycrystalline fayalite under conditions of simultaneous high pressure and high temperature, weakens the case for a martensitic olivine⇌spinel transformation mechanism.

Microprocessor based air inflation control system

Abstract: A microprocessor based system for monitoring the air pressure within an inflatable device and controlling the supplying of air to or venting of air from the device, as needed. A microprocessor based system controller includes controls for setting a desired air pressure signal and an input for receiving an actual air pressure signal from a pressure transducer connected to the inflatable device. If the desired air pressure signal is less than the actual air pressure signal, the system controller provides a vent control signal for application to an air vent control device to cause venting of air from the inflatable device. If the desired air pressure signal is greater than the actual air pressure signal, the system controller provides a fill control signal for application to an air inflating device to provide air to the inflatable device. In addition, the system controller provides a compressor actuation signal for application to an air compressor to provide air to the air inflating device as needed and an intermittent indicator signal for indicating provision of air to or venting of air from the inflatable device. The fill and vent control signals are of durations determined by the difference in the desired air pressure and the actual air pressure, following which the actual air pressure is again monitored and compared with the desired air pressure and, if appropriate, the filling or venting cycle repeated.

Effects of the pressure perturbation field in numerical models of unidirectionally sheared thunderstorm convection - Two versus three dimensions

Abstract: The physical roles of 'buoyant' and 'dynamic' pressure components, and the distinction between buoyant and hydrostatic pressure perturbations, are aspects of the pressure perturbation field in strongly sheared convective storms studied by means of two- and three-dimensional anelastic numerical modeling experiments with common environmental profiles. The pressure analysis clarifies the differences between two- and three-dimensional storms. In the main updraft, strong midlevel thermal buoyancy is partly opposed by a downward-perturbed vertical pressure gradient force. This, however, occurs to a much greater extent in two dimensions than in three, contributing to smaller net upward accelerations. While the buoyant and hydrostatic fields are intimately related to the total buoyancy distribution, the buoyant pressure perturbation is smoother and of lower amplitude than its hydrostatic counterpart. For the model experiments, this distinction is far greater in three dimensions than in two, in association with the smaller scale of the active convection in three dimensions.

Measuring barometric pressure with a manifold pressure sensor in a microprocessor based engine control system

Abstract: A method of measuring barometric pressure with a manifold pressure sensor (62) in a microprocessor based engine control system utilizes known engine operating conditions to interrogate the sensor. Also on engine turn-off, a power latch signal (158) is generated to delay power removal until the throttle valve (160) is driven open and the pressure sensor (62) is interrogated for its value. This value at this time is the ambient or barometric value of pressure. This value is stored in the microprocessor's (26, 28) memory (84, 86) and maintained by means of a standby voltage (80). During engine operation, the pressure sensor (62) is interrogated and value of the stored barometric pressure is changed by one unit of pressure if the stored and measured values are unequal.

Thomson Scattering as a Diagnostic of Atmospheric Pressure Discharges

Abstract: Thomson scattering is reviewed as a diagnostic technique for the determination of electron energy distributions and concentrations in a plasma. Both theoretical and experimental aspects are considered, and scattering spectra which would be expected for high voltage spark discharges and inductively coupled plasmas at atmospheric pressure are computed. A nonlinear method bearing the same relationship to Thomson scattering as CARS does to linear Raman spectroscopy is mentioned, and its properties are compared to the more common linear Thomson technique. Related plasma diagnostics involving high power laser scattering are also discussed.

Liquid volume sensor system

Abstract: This invention relates to apparatus for determining the amount of liquid in a tank by measuring the pressure at the bottom and at a height above the bottom of the tank, and provides apparatus for compensating for apparent volume measurement variations caused by expansion and contraction of the tank and liquid with variation in temperature. A tube which expands in length at an exactly compensating rate varies the height of the second pressure sensor relative to the first. A further embodiment is a pneumatic system which avoids the necessity to immerse the pressure sensor, and utilizes an inexpensive single differential pressure transducer instead of two, and which cancels out the effect of any changes in zero setting of the transducer, changes in sensitivity of the transducer, or changes in atmospheric pressure.

Production of oxygen enriched air

Abstract: A pressure swing adsorption process is provided for the direct production from ambient air of a moderately enriched oxygen product gas. The production of a product gas having an oxygen concentration of 23 to 30% is effected by a three step cycle wherein (1) the feed air is charged to a bed of nitrogen selective adsorbent until the bed is brought from atmospheric pressure to a pressure in the range of up to 10 atmospheres, (2) reducing the bed pressure to an intermediate level by withdrawal of oxygen enriched product gas therefrom and (3) finally venting the bed to restore atmospheric pressure. By an alternative mode including a fourth step of purging the bed following the venting step, a product of 23 to 45% oxygen concentration is obtained.

Carbon Dioxide: A Biogeochemical Portrait

Abstract: Carbon dioxide, chemical formula CO2, is a colorless and tasteless gas about 1.5 times as heavy as air. Its specific volume at atmospheric pressure (101, 325 N m-2) and room temperature (21 °C) is 0.546 m3 kg-1. Under natural atmospheric conditions it is a stable, inert, and nontoxic gas. When subjected to higher pressure and temperature, the gas can be liquefied and solidified. For instance at 21 °C and 838 psig (= pounds per square inch gage), CO2 becomes a liquid. Further cooling will result in the formation of dry ice snow, which at atmospheric pressure has a sublimation temperature of — 78 °C.

Vanadium oxidation as a result of cw CO2 laser irradiation in atmospheric air

Abstract: New results are reported concerning the vanadium oxidation by cw CO2 laser irradiation in air at atmospheric pressure. Particular emphasis is paid both to the initial stage and the development of the oxidation process under the action of the laser radiation. Some aspects are finally discussed concerning the quantitative theoretical interpretation of the experimentally recorded data.

Aerodynamic effect of combustor inlet-air pressure on fuel jet atomization

Abstract: Mean drop diameters were measured with a recently developed scanning radiometer in a study of the atomization of liquid jets injected cross stream in high velocity and high pressure airflows. At constant inlet air pressure, reciprocal mean drop diameter, was correlated with airflow mass velocity. Over a combustor inlet-air pressure range of 1 to 21 atmospheres, the ratio of orifice to mean drop diameter, D(O)/D(M), was correlated with the product of Weber and Reynolds number, WeRe, and with the molecular scale momentum transfer ratio of gravitational to inertial forces.