Showing papers on "Total pressure published in 1972"

The Flow in S-shaped Ducts

Abstract: Measurements are presented of total pressure, static pressure, surface shear stress and yaw angle in the flow through several S-shaped ducts, each with a thin turbulent boundary layer at entry. The results show that the region of low total pressure in the exit plane, found by previous workers, is due to expulsion of boundary-layer fluid by a pair of contra-totating vortices in the boundary layer. The generation of these vortices is explained: similarly-produced vortices, with similar effects, occur in some types of wind-tunnel contraction and possibly in other three-dimensional flows.

Kinetics of Thermal Growth of Ultra‐Thin Layers of SiO2 on Silicon I . Experiment

Abstract: The rate of formation of very thin films thermally grown on [111] and [100] oriented silicon wafers was studied using ellipsometry to measure oxide thickness. Film thicknesses from 10–300Aa were obtained by varying oxidation time, oxidation temperature (700°–1000°C), and oxygen concentration in O2‐N2 mixtures at 1 atm total pressure. The applicability of ellipsometry for such a study is discussed. Reproducibility of oxide films grown to thicknesses of 20–30Aa was approx. ±1.0Aa. Under otherwise equal conditions the oxide thickness grown differs for [100] and [111] oriented wafers. The pressure and temperature dependence of the linear rate constant, klin, show that the growth reaction is more complicated than was suggested earlier. In particular, a different pressure dependence for the two substrate orientations used indicates that several oxygen species participate in the rate determining steps.

Measurements of water pressure in moulins as part of a movement study of the White Glacier, Axel Heiberg Island, Northwest Territories, Canada

Abstract: In 1970 water pressure was measured in several moulins on the White Glacier. Pressure variations in some moulin channels extended over the full measuring range of the instruments (0–1 and 0–2 bar above atmospheric pressure), even at depths of less than 50 m below the surface. Measurements at different depths showed that total pressure variations were sometimes greater than this. The pressure data are compared with variations in the surface velocity of the glacier.

Kinetics of Reactions Leading to O2‐(H2O)n in Moist Oxygen

Abstract: Most of the rate constants for the reactions by which O2− and O− are converted to the hydrates O2−(H2O)n and O3−(H2O)n in moist oxygen were determined with a high pressure mass spectrometer utilizing a pulsed electron beam ion source. The total pressure range was 0.6–7 torr and most reactions were investigated at room temperature.

A comparison of disturbance levels measured in hypersonic tunnels using a hot-wire anemometer and a pitot pressure probe.

Abstract: Disturbance levels were measured in the test section of a Mach 5 blowdown jet using a constant-current, hot-wire anemometer and a pressure transducer. The disturbance levels, measured by the two instruments and normalized by local mean values, agreed within about 30%, with the pitot data higher than the hot-wire data. The rms disturbance levels measured with the hot-wire anemometer and converted to pitot pressures using a quasi-steady flow analysis, were about two-thirds the levels measured with the pitot probe. The variation of the normalized rms disturbance levels with stagnation pressure indicated that transition occurred in the boundary layer on the nozzle wall and influenced the outputs of the instruments located at the exit of the nozzle when the total pressure was about 35 N/sq cm. Below this pressure the disturbance levels decreased markedly. At higher pressures the disturbances were predominantly aerodynamic noise generated by the turbulent boundary layer on the nozzle wall.

Performance of tandem-bladed transonic compressor rotor with tip speed of 1375 feet per second

Abstract: The design and experimental performance of a 20-inch diameter tandem-bladed axial-flow transonic compressor rotor is presented. Radial surveys were made of the flow conditions. At design speed the peak efficiency was 0.88 and occurred at an equivalent weight flow of 63 pounds per second. At peak efficiency the total pressure and total temperature ratios were 1.77 and 1.20, respectively. The stall margin at design speed was 10 percent based on weight flows and total pressure ratios at peak efficiency and near stall.

Computation of Shocked Flows in Compressor Cascades

Abstract: A numerical technique is presented for the calculation of shocked flows in compressor cascades. The problem is posed in the time-dependent form and the asymptotic solution at large times provides the solution of the steady physical problem. The solutions exhibit the formation and movement of shocks as the static pressure ratio across the cascade is varied. The resulting inlet and outlet angles and total pressure loss are also shown.Copyright © 1972 by ASME

Viscosity of nitrogen gas at low temperatures up to high pressures: A new appraisal

Abstract: The absolute viscosity of nitrogen gas was determined experimentally for the pressure and temperature range 1 to 150 atmospheres and 90°K to 400°K respectively. The maximum error in the data presented is believed to be better than ±1.5%, and ±1% for the high and low pressure data respectively. Two general correlating equations, one for atmospheric pressure and the other for all the available high pressure data, (i.e. densities up to 0.4 g/cc or 1.5 ρ (critical)) are presented, together with a table of recommended smoothed data, which are felt to be accurate to ±1.5% or better. Values for the low velocity collision diameter σ and maximum energy attraction functions are also presented for the low pressure data.

The rate of vaporization of tungsten in argon

Abstract: The vaporization kinetics of thin tungsten wires has been measured under natural convection conditions in high-purity argon. The rate was determined as a function of argon pressure and filament temperature in the range between 80 and 300 mm and 2850 and 3150 K. The vaporization rate is exponentially related to temperature with an activation energy of approximately 190 kcal/mole and inversely proportional to total pressure to the 0.87 power. The activation energy predicted by stagnant-film mass transfer theory is 202.5 kcal/mole, while the theoretically predicted inverse pressure dependence is 0.90. The rate was also sensitive to reactive impurities in the argon; thus,in situ, purification of the atmosphere was required.

Heating device for flow sondes

Abstract: This invention relates to an improvement in a flow sonde, particularly for measuring aerodynamic values in aircraft such as the total pressure, the static pressure and the total temperature. The improvement comprises thermally controlled resistor means in the sonde body, said means having a low increase of resistance within a specific temperature range and a high increase of resistance in an adjacent range, whereby there is obtained a high heating power at a low ambient temperature and a limitation of the power absorption when a predetermined temperature is reached.

Interpretation of Pitot Pressure in Compressible Two-Phase Flow

Abstract: An analysis is presented of the dynamics of small droplets near the mouth of a purged or unpurged pitot tube in two-phase flow. Under certain conditions, that part of the total pressure which is at...

Stark-effect modulation of co{11 {11 laser with nh{11 d

Abstract: The molecular stark-effect in NH2D is used to modulate the 10.6 Mu , P(20) line of a CO2 laser. A 25 cm cell external to the laser is filled with about equal parts of NH3 and ND3 to a total pressure between 2 and 10 torr. An equilibrium concentration of NH2D as high as 45 percent is rapidly achieved. The cell is biased with a DC field (3.8 + OR - 0.1 KV/cm) and modulated with an AC signal of (about 20 V RMS). At a cell pressure of 4 torr, a modulation depth of 40 percent is achieved.

High‐Pressure Pulsed CO2 Chemical Transfer Laser

Abstract: The exothermic chain reactions between deuterium and fluorine have been used to produce intense laser emission from carbon dioxide in a high‐pressure pulsed transfer laser. Stable mixtures of D2–F2–CO2 diluted in He and cooled to −60°C were used as a fuel. Reactions initiated by flash photolysis of this system produced 10.6‐μm radiation with peak power of 200 kW and total energy of 5 J in dilute mixtures at total pressures up to 1 atm. The output power, laser pulse duration, and time of maximum gain are found to be strongly dependent on partial pressures of the constituents, total pressure of reactive components, nature of the diluents, and degree of refrigeration of the mixture.

Continuous‐Wave Overtone Bands in a CS2–O2 Chemical Laser

Abstract: The carbon monoxide overtone band has been observed in a continuous‐wave (cw) CS2–O2 chemical laser. A total of fifteen vibrational transitions have been resolved in the region between 2.3 and 2.9 μ. The influence of the total pressure has also been studied.

Piston manometer as an absolute standard for vacuum-gauge calibration.

Abstract: Total pressure in a calibration volume is determined by measuring the force on a thin circular disk, of accurately known area, that is freely suspended in a hole in the container wall, so that the disk is substantially flush with the wall. The disk almost fills the hole, so that there is a narrow annular gap. A continuous flow of calibrating gas, injected into the container in order to maintain a desired pressure, passes through the annular gap to a diffusion pump. The ratio of pressures on the two faces of the disk is of the order of 100:1, so that downstream pressure need be known only nominally in order to deduce the upstream pressure. Force on the disk is measured by a balance that is calibrated in situ with dead weights. In one arrangement, pressures in the range of 10–500 μTorr were measured with an estimated probable error of (1μTorr+1%).

Magnetostatic Equilibria of Finite‐Pressure Minimum‐ B Plasma Configurations

Abstract: Magnetostatic equilibria for a broad class of plasma conditions are shown to correspond to solutions of the equations ∇·B = 0, ∇× H =0, where B = μ H. Magnetohydrodynamic stability then corresponds to satisfaction of the criteria H>0 and dH/dB>0, where B = |B | and H =μ−1B. Equilibria are studied for a variety of plasma distributions taken as functions of total energy and magnetic moment and in the most general cases, the coordinates of a line of magnetic flux. A new result is the determination of a relationship between well depth and the maximum pressure for magnetohydrodynamic stability which puts an upper limit on the well depth to achieve given pressure when the value of the maximum field strength is fixed. For so‐called collisional distributions, if p is the total pressure at the center and B0 is the maximum magnetic field, β = 8πp/B02<0.2, and the mirror ratio to achieve maximum β may not exceed 1.8. More general equilibria, where the pressures are functions of field lines as well, cannot improve ...

Aerodynamic and Acoustic Performance of Two Choked-Flow Inlets Under Static Conditions

Abstract: Tests were conducted to determine the aerodynamic and acoustic performance of two choking flow inlets under static conditions. One inlet choked the flow in the cowl throat by an axial translation of the inlet centerbody. The other inlet employed a translating grid of airfoils to choke the flow. Both inlets were sized to fit a 13.97 cm diameter fan with a design weight flow of 2.49 kg/sec. The inlets were operated in both the choked and unchoked modes over a range of weight flows. Measurements were made of inlet pressure recovery, flow distortion, surface static pressure distribution, and fan noise suppression. Choking of the translating centerbody inlet reduced blade passing frequency noise by 29 db while yielding a total pressure recovery of 0.985. Noise reductions were also measured at 1/3-octave band center frequencies of 2500, 5000, and 20,000 cycles. The translating grid inlet gave a total pressure recovery of 0.968 when operating close to the choking weight flow. However, an intermittent high intensity noise source was encountered with this inlet that precluded an accurate measurement of inlet noise suppression.

Effects of transverse ribs on pressure recovery in two-dimensional subsonic diffusers

Abstract: : An experimental investigation was conducted to evaluate the performance of two-dimensional ribbed diffusers. Static pressure recovery of a straight wall diffuser and a corresponding ribbed diffuser was obtained over a wide range of diffuser total angles and subsonic Mach numbers for three diffuser length-to-throat width ratios. At selected geometries, total pressure recovery and distortion index were obtained. In addition to an optimum rectangular rib design, obtained from earlier water table flow visualization test, a chamfered rib and a roughened surface insert were also tested. A high response pressure transducer was used to detect pressure fluctuations occurring within one of the inter-rib cavities.

A Procedure for the Design of Complex Distortion Screen Patterns for Producing Specified Steady-State Total Pressure Profiles at the Inlet of Turbine Engines

Abstract: : A technique was developed for the design of distortion screens which will produce a specified steady-state total pressure profile at the inlet of a turbine engine. The design technique is discussed, and sample results of its application are presented. The influence of the distortion screens on wall static pressure upstream of distortion screens is discussed, and the total pressure distortion from a 180-deg solid plate is presented. Measured total pressure loss is presented for screen of various porosity.

Tantalum Films Triode-Sputtered in Mixtures of Argon and Water Vapor

Abstract: Tantalum films have been deposited in a triode sputtering system operating at a total pressure of 5×10−4 Torr that was maintained by continuously adding an argon-water vapor mixture. Because of the low operating pressure, a mass spectrometer mounted directly in the chamber was used, without any differential pumping, to monitor mass spectra before, during, and after sputtering. The mass spectra show that the water vapor is dissociated in the discharge, and the resultant oxygen is gettered into the film. The oxygen content of the films was determined from the anodization efficiency, and it increased linearly with the inlet rate of water vapor. Measurements of the electrical properties show that the oxygen is incorporated in the films in the same way for water vapor and oxygen doping. The resistivity is increased from 50 to 1014μΩ cm with increasing oxygen content. The rapid increase in resistivity from 50 to 200 μΩ cm between 4 and 11 at.% is due to the change from bcc to the β-Ta structure. These results s...

Method and apparatus for determining the thrust of a jet engine

Abstract: Apparatus is known for determining gross thrust in jet engines by measuring various internal pressures, including measurement of total pressure at the nozzle entrance by means of an immersed probe. The immersed probe has a very short life when an afterburner is used in the engine. The apparatus for the invention is able to determine total pressure at the nozzle entrance, without an immersed probe, from the total pressure in the diffuser and the static pressure at the nozzle entrance. Another embodiment makes use of an additional static pressure in the flameholder region. Also, the invention is for determining the gross thrust of an engine and it distinguishes between an engine with a nozzle operating in a choked condition and an unchoked condition.

Electrical distribution transformer having pressure relief means

Abstract: High internal pressure within a distribution transformer casing caused by an incipient fault or thermal overload is a hazard to the lineman, and the transformer is provided with a pressure relief valve which opens automatically to limit the total pressure rise within the casing or may be actuated manually by the lineman to vent the casing even though the internal pressure is below the operating level of the relief device. A die cast plug alternatively may be used to seal the transformer casing or may be formed in a simple machining operation into the pressure relief device valve body with an integral valve seat and an integral valve stem guide.

Vibrational Relaxation Times of Oxygen and Oxygen Mixed with Several Light Gases

Abstract: Vibrational relaxation times of τ of oxygen have been determined from sound absorption measurements in the pressure range from 14 to 35 atm. Values of τ−1 were found to increase more rapidly with increasing pressure than the linear dependence expected if binary collisions alone were important. The effect of adding trace amounts of H2, He3, and He4 at a total pressure of 35 atm was also studied. Resulting relaxation times for O2–H2 and O2–He4 collisions were found to be in good agreement with earlier data at lower pressures. He3 was found to be 3.5 times more efficient than He4 in exciting vibration in O2.

Hypersonic Turbulent Boundary Layer with Pressure Gradients and Cross Flow

Abstract: J experimental and theoretical investigation of the hypersonic compressible turbulent bounary-layer undergoing both normal and longitudinal adverse pressure gradients and cross flow is presented. The investigation is confined to the plane of symmetry on a compression flare in order to simulate the conditions existing at the centerline on an inlet of a jet engine. The cross flow is induced by connecting two lateral curved plates symmetrically on the sides of the flare. The integral equations of the compressible turbulent boundary-layer, which include terms referring to the cross flow, are solved numerically. Content The experiments were performed in a Mach 6 blowdown axisymmetric wind-tunnel, with a stagnation temperature of 800°R, a stagnation pressure of 1900 psia, and a freestream Reynolds number of 4.4 x 10 7 per foot. The model consisted of a streamlined centerbody followed by a compression flare 6.3 in. in length. The maximum turning angle of the flare was 43°. The over-all axial length of the centerbody, from the nozzle throat to the test section, was 77.3 in. The compression flare was equipped with pressure taps to measure the longitudinal and the peripheral pressure distributions, and thermocouples were used to measure the heat-transfer rates at the wall. The static pressure, total pressure, and total temperature profiles in the direction normal to the compression flare were measured with traversing probes at nine locations along the flare. Subsequently, the compression flare was cut laterally to connect two lateral curved plates symmetrically placed on each side of the flare to create an expansion in the peripheral direction and establish a favorable cross flow (C.F.), in addition to the normal and longitudinal pressure gradients. Because of the large variation in the turning angle of the flare, the wall pressure increases from the freestream static pressure to a value approximately fifty times greater. The tests show no separation of the naturally established thick turbulent compressible boundary-layer along the centerbody. With the same initial conditions at the beginning of the compression flare, an inviscid method of characteristi cs solution shows that the compression waves coalesce into a shock outside the boundary-layer at the terminal part of the compression flare.