Showing papers on "Total pressure published in 1968"

Fluid flow through woven screens

Abstract: A packed bed model has been adopted to develop a general correlation applicable to the flow of Newtonian fluids through all types of woven metal screens. Both of the main theoretical approaches to studying pressure drop in packed systems have been used by visualizing the screen as a collection of submerged objects with surface area to unit volume ratio a for laminar flow, and as a bundle of tubes of diameter D for turbulent flow. In the usual manner viscous and inertial energy losses are added to give an expression for the total pressure loss. Rearrangement of the general equation to the form of a friction factor yields a unique definition of the Reynolds number for screens NRe = ρu/μa2D. Procedures are described for collection of pressure drop-velocity data for the flow of nitrogen and helium through plain square, full twill, fourdrinier, plain dutch, and twilled dutch weaves. The data are used to derive a viscous resistance coefficient α = 8.61 and an inertial resistance coefficient β = 0.52. The validity of the correlation equation is tested by using additional data from the literature. The correlation successfully predicts pressure drop for a Reynolds number range of 0.1 to 1,000, void fractions from 0.35 to 0.76, screen pore diameters from 5 to 550 μ, mesh sizes from 30 to 2,400 wires/in., and surface area to unit volume ratios from 1,200 to 29,000 ft.−1.

The mechanism of reactive sputtering

Abstract: The reactive sputtering of tantalum in mixed argon/oxygen atmospheres at a total pressure of 3.0×10−4 torr has been investigated by means of measurements on deposition and growth rates, density, electrical properties and electron diffraction. The main controlling factor on all of the parameters was found to be the partial pressure of oxygen.

Fluorine and Proton NMR Study of Gaseous Hydrogen Fluoride

Abstract: The 19F and 1H resonances for gaseous hydrogen fluoride were measured over the range from low pressure to saturated vapor. In each spectrum, only a single line is observed, which shows an unusually large and monotonic change in chemical shift with HF density. The monomer chemical shifts were determined by extrapolation, to zero total pressure, of data for mixtures with various foreign gases. The 19F chemical shifts, in parts per million relative to SiF4 gas at zero pressure, are HF (g, monomer): 46.85 ± 0.35 ppm, DF(g, monomer): 49.35 ± 0.35 ppm, HF (liq, cylinder): 25.53 ± 0.04 ppm. The 1H shifts relative to CH4 gas at zero pressure are HF(g, monomer): − 2.10 ± 0.20 ppm, HF (liq, cylinder): − 8.67 ± 0.02 ppm. These data are for 34°C, but the extrapolated monomer shifts appear to be practically independent of temperature. The absence of spin‐spin splittings, and the observation of only a single averaged resonance in HF‐DF mixtures, proves that there are rapid monomer‐breaking exchange processes in the vap...

Experimental Investigation of Laminar Near Wakes Behind 20 Wedges M=6

Abstract: An experimental investigation at Mm = 6 has been conducted to determine mean-flow properties in near wakes behind several 20° included- angle wedges at zero angle of attack. One cold-wall (H = 0.3 in., TW/TQ = 0.19) and two adiabatic-wall (H = 0.15 in., H = 0.3 in.) configurations were tested. Freestream Reynolds numbers were varied from 0.5 X 10 5 to 2 X 105 per in. for each model. Flowfield mappings and flow-property profiles were obtained in the base region for the wedge of 0.3-in. base height with and without cooling by combining Pitot- pressure data with total temperature and mass flux results from hot-wire measurements. The variation of total pressure along streamlines was initially negligible during the shearlayer turning process. Downstream boundaries of these isentropic turns corresponded to viscous-layer edges that were positioned in the outer portions of the shear layers, indicating that wake shocks originated from within viscous regions of the shear layer.

Experimental studies in magneto-fluid dynamics - Pressure distribution measurements around a sphere.

Abstract: Measurements of the pressure distribution around a sphere placed in aligned magnetic and velocity fields show that an increase in drag is mainly due to a decrease in the pressure on the base of the body. When magnetic forces are large compared to inertia forces, this decrease is due to a loss in total pressure along streamlines just outside the surface boundary layer and an acceleration of the flow to a velocity much larger than the reference velocity. Separation of a viscous boundary layer takes place behind the equator and still, to a large extent, controls the magnitude of the base pressure and the drag experienced by the sphere. A model consistent with these findings is presented.

Density Disturbance ahead of a Sphere in Rarefied Supersonic Flow

Abstract: An electron‐beam x‐ray technique was used to obtain precise measurements of the density along the stagnation streamline of spherical models tested in a M = 4.2 (nominal Mach number) nitrogen stream and a M = 3.8 argon stream. Variation of the total pressure and the model radius provided a Re range (based on free‐stream properties and model radius) of 30‐500 in nitrogen, 100‐2000 in argon. The measurements were made with model surface temperatures of 300° K (equal to the total temperature of the flow) and 78° K.

Attenuation of circumferential inlet distortion in multistage axial compressors.

Abstract: Circumferential inlet distortion in a high hub-tip ratio multistage machine is treated by analyzing the compressor as a region in which a large number of small stages produce a pressure rise that is a function of the local mass flow rate. The resistance to circumferential flow due to the blading is included through an empirical factor. It is found that the over-all attenuation of both total pressure distortion and axial velocity distortion is mainly dependent on the slope of the compressor pressure rise vs flow rate characteristic. The attenuation increases when the slope of the characteristic is made more negative. In addition, considerable flow redistribution is found to occur upstream of the compressor. The theory has been compared with interstage data obtained on a three-stage, low-speed compressor with axial clearances that are 26% of the total length and a hub-tip ratio of 0.675. It is found that the approximation of zero axial clearance (infinite resistance to circumferential flow) gives excellent results. In consequence, it appears that for the normal range of axial clearances, the circumferential flow within the compressor can be neglected in a first-order analysis of the effects of inlet distortion.

Liquid-vapour equilibrium of the system nitrogen + argon at pressures up to 10 atm

Abstract: A static method has been used to determine vapour pressures and compositions of the system nitrogen + argon at pressures up to 10 atm. Equations expressing the variation of relative volatility and condensation pressure with temperature and composition are given for the range 80–105°K. The results have been tested for thermodynamic consistency and are compared with those of previous workers. Smoothed vapour pressures and excess free energies of mixing calculated from the data show reasonable agreement with the precise total pressure results of Pool et al. for the lower pressures.

Pressure and current dependent shifts in the frequency of oscillation of the co2 laser

Abstract: The shift of the frequency of oscillation of the 00°1–10°0 rotation‐vibration band at 10.6 μ of a CO2 laser has been investigated as a function of total pressure, CO2 partial pressure, discharge current, and cavity mode position. The measurements were made by heterodyning two passively stabilized CO2 lasers, both oscillating in a single transverse mode and single frequency at the P branch of the 00°1–10°0 rotation‐vibration band of CO2. The result yielded a 5–8 MHz/torr frequency shift toward red due to an increase in total pressure and a 500–900 kHz/mA shift toward blue due to an increase in excitation. The amount of frequency shift due to excitation was found to be independent of the location of the cavity resonance with respect to the Doppler center. The dependence on CO2 partial pressure was also determined.

Gaseous atmosphere control device

Abstract: A CONTROL SYSTEM FOR MAINTAINING THE COMPOSITION AND PRESSURE OF A GAS MIXTURE INCLUDING OXYGEN AT A PREDETERMINED TOTAL PRESSURE IN A CHAMBER AND SIMULTANEOUSLY MAINTAINING THE PARTIAL PRESSURE OF AT LEAST THE OXYGEN AT A PREDETERMINED LEVEL RELATIVE TO THE TOTAL PRESSURE OF THE MIXTURE. THE CONTROL SYSTEM IS CAPABLE OF PREFERENTIALLY SUPPLYING OXYGEN FROM A SOURCE TO THE CHAMBER WHENEVER THE OXYGEN PARTIAL PRESSURE IS BELOW THE PREDETERMINED LEVEL AND SUPPLYING A SECOND GAS FROM A SOURCE WHEN THE TOTAL PRESSURE IS BELOW THE PREDETERMINED LEVEL WHILE THE OXYGEN IS AT THE PREDETERMINED PARTIAL PRESSURE LEVEL.

Oxidation of Ethylene by the Photolysis of NO2 at 25°C

Abstract: Ethylene was irradiated at 3660 A in the presence of NO2 at 25°C. Quantum yields were determined as a function of ethylene pressure, NO2 pressure, and the total pressure (using N2). The quantum yields for NO2 dissociation increased as a function of (C2H4) and approached a value greater than 2. The main features of the proposed mechanism are the addition of oxygen atoms to ethylene producing an energy‐rich intermediate which dissociates into CH3 and CHO. This is followed by rapid reaction of the radicals with NO2 to produce the stable products.

Hydrothermal Studies of Garnet — Mica Equilibria in the System 3(FeO, MnO)— 2 Al2O3—12 SiO2—K2O—H2O

Abstract: The system has been studied under a constant pressure of 3600 atm. and within a temperature range between 450° and 720°. Oxygen fugacity has been controlled with quartz-fayalite-magnetite buffer. The proportion Fe2+ and Mn2+ has been varied while other components have been kept at a constant ratio. The experimental results are visualized in a phase diagram (Fig. 2). The most important equilibrium, annite+muscovite+3 quartz=garnet+2 sanidine+2 H2O has been treated thermdynamically. The heat of reaction is about 49 kcal. Based upon this value, the heat of formation for almandite garnet is — 84 kcal/mole. Curves have been constructed for in garnet. The first one shows the variation in composition of garnet with the fugacity of water when total pressure is kept constant at 3000 atm. The latter curve shows the corresponding variation with total pressure, where Pt=PH2O+PH2.

Pressure Measurements in a Magnetically Driven Shock Tube

Abstract: Measurements of total pressure and static pressure were taken in a magnetically driven shock tube at an Alfven Mach number of M1≈0.66 in air at an initial pressure range of 50–200 μHg. Total pressure measurements ranged from 0.3–0.8 of the Newtonian pressure based on an equilibrium real gas density ratio. A small separation between the shock and drive current sheet was detected over the range of initial pressures, but was not always repeatable. The static pressure was measured and found to be approximately equal to the drive magnetic pressure.

Air compressor surge control apparatus

Abstract: 1,223,490. Axial-flow compressors. BENDIX CORP. Dec.30, 1968 [Jan.2, 1968], No.61643/68. Heading F1C. [Also in Division G4] Surge control apparatus for a multi-stage axialflow compressor 24, Fig. 1, of a gas turbine engine 20, comprises a normally closed air bleed valve 72 which is opened when surge is imminent in accordance with the relationship Ptx-Psx# K(Pt 3 -Pt 2 ), where Pt 3 is pressure derived from compressor outlet total air-pressure, Pt 2 is compressor inlet total air-pressure, Ptx and Psx are air-pressures derived from total and static air-pressures respectively both taken at the compressor inlet or outlet, and K is a constant. Inlet total pressure and outlet total and static pressures are communicated to first, second and third diaphragm-separated chambers 36, 38, 40 respectively through lines 52, 56, 60 to regulate the position of a servovalve 46 controlling the venting through line 86 of pressurized air from a chamber 84 to control the pressure Px therein and thereby control the air bleed valve 72. In an alternative embodiment, Fig.2 (not shown), the first diaphragm-separated chamber contains an evacuated bellows (116) connected to the diaphragms and to a lever-type servovalve (122) by a rod (114). Moreover, the first chamber is connected to the inlet and outlet total pressures through a respective restrictor, the second chamber is connected to outlet total pressure, and the third chamber is connected to outlet static pressure. The latter two pressures may be sensed in a Venturi (102) or in a diffuser. In another embodiment, Fig.3 (not shown), the first chamber is connected to the inlet static and outlet total pressures through a respective restrictor, the second chamber is connected to the inlet static pressure, and the third chamber is connected to the inlet total pressure. A final embodiment, Fig. 4 (not shown), employs fluidic means to directly control the pressure differential across a diaphragm (200) controlling the air bleed valve, the power jet of the fluidic means being subjected to two opposing transverse control jets connected respectively to inlet total pressure and, through respective restrictors, to inlet static and outlet total pressures.

Graphical representation of homogeneous chemical equilibria in volcanic gas systems

Abstract: The logarithms of the partial pressures of the components of the gaseous phase are plotted against the logarithm of the partial pressureof the oxygen under conditions of constant temperature, constant total pressure, and constant ratios of all elements except oxygen. The result is a quantitative survey of the effect of oxidation on the gases present. The equilibrium composition of an individual volcanic gas sample or of any mixture of gases may be obtained from the diagram when the atomic ratio of the oxygen is also fixed. In constructing logarithmic partial pressure diagrams, it is essential to know which molecular species may become dominant (contain virtually all of a certain element) under the conditions of the diagram.

Instrument for measurement of partial pressure of components in a fluid mixture

Abstract: A system providing an output signal linearly related to the amount of one selected component present in a mixture of fluids having at least two components. The system includes at least two detectors, one producing an output signal which may be expressed as the sum of two terms where the first term varies in linear proportion to variations in the partial pressure of the selected component and the second term varies in proportion to the variations in the total pressure of the fluid independent of its composition. The second detector produces an output which varies in proportion to variations in the total pressure of the mixture, independent of its composition. The two signals are then combined to produce an output signal which varies linearly with the amount of the selected component, independent of variations in the total pressure of the mixture.

Diffusion Coefficients in Hydrocarbon Systems. Homogeneous Phases at Elevated Pressures

Abstract: The phenomenon of change in pressure accompanying gaseous diffusion in a closed isochoric, isothermal system has been studied experimentally and theoretically. Special equipment has been developed for measuring pressure differences with an accuracy better than 0.01 p.s.i. at total pressure levels of hundreds of pounds per square inch. The theoretical analysis shows that as the system approaches equilibrium, the pressure as a function of time assumes the simple exponential form p - p_(eq) = -ae^(-bD_(12)t, where p_(eq) is the equilibrium pressure, D_(12) is the binary diffusion coefficient, a is a thermodynamic quantity, and b is a constant depending on the size and shape of the diffusion cell. This expression can be used for the determination of D_(12) from pressure-time measurements. Measurements upon the system CH_4-C_3H_8 at T = 160° F. and p_(eq) = 570 p.s.i. have shown the applicability of this method, but more experimental work is required for ascertaining its accuracy.

Probing techniques for use in high temperature reacting flows

Abstract: : A basic probe has been designed which consists of a 1/8-in.-diam, water-cooled copper probe with an inside diameter of 0.050 in. These probes may be aspirated to take a gas sample and temperature reading, or used without aspiration to measure total pressure. Two systems currently being investigated to measure temperature are quartz-coated thermocouples and pneumatic thermometers. These probe designs were chosen because they should not include the heat of recombination of non-equilibrium gases in the temperature reading as would a calorimeter-type total enthalpy probe. The gases are analyzed on line with a bistable fluid oscillator having an oscillation frequency that is a function of the molecular weight of the sample. No quantitative theory of fluid oscillators is available; however, observations are given of the effect of some of the design parameters on performance. A study was made of the effect of probe shape and Mach number on the validity of samples taken in a supersonic stream. For hydrogen-nitrogen mixtures at a static pressure of 1 atm, no change between the free stream and the sample was seen in any of the tests.

Letters: Piezometer for Monitoring Rapidly Changing Pore Pressures in Saturated Clays

Abstract: A modified Imperial College Piezometer incorporating a differential pressure transducer is a highly sensitive pore pressure measuring device unaffected by the total pressure of the environment in which it is placed. It is sufficiently rugged for field installation and provides the option of field calibration in situ.

Influence of the initial boundary layer on base pressure

Abstract: The base pressure pb, for an initial turbulent boundary layer, is determined for supersonic nonisothermal flow about a two-dimensional backward-facing step. This problem has been considered previously. In solving it in [1, 2], use was made of the Korst condition [3], which assumes equality of the total pressure pj* on the line of constant mass to the pressure behind the closing oblique shock. However the pressure at the reattachment section p* is lower than that behind the closing shock by 30–40% [4], and consequently the Korst condition is inaccurate. Therefore in the references cited only qualitative agreement with experiment was obtained. In contrast with [1, 3], Nash [5] introduces p*; however, it is defined by an empirical coefficient. In the present study, to find pb we make use of the condition of conservation of mass in the base region, written in the form of the equality pj*=p*, where p* is defined from the assumption of minimum thickness δ of the dissipative layer at the reattachment section.

The pyrolysis of tetrafluoroethylene

Abstract: : The pyrolysis of tetrafluoroethylene was studied in the temperature and pressure range 300 to 455C and 25 to 760 torr. The rate of reaction was determined to be second order with respect to the tetrafluoroethylene, and three independent numerical values of the second order rate constant were determined by simultaneously measuring the tetrafluoroethylene concentration, the octafluorocyclobutane concentration and the total pressure as a function of reaction time. The temperature dependence of the reaction rate constants are given. (Author)

Axial flow compressor design computer programs incorporating full radial equilibrium. Part 2 - Radial distribution of total pressure and flow path or axial velocity ratio specified /program 3/

Abstract: Axial flow compressor design computer programs incorporating radial distribution of total pressure and flow path or axial velocity ratio

Anode nozzle effects on the bulk properties of arc-heated argon

Abstract: : The thrust produced by a Gerdien-type d-c arc-jet using argon gas and exhausting into a low-pressure (approximately 2 mm Hg) test cell was measured and used to determine the momentum losses which occurred in the constant area anode nozzle. From these losses, a loss coefficient is defined which will yield good approximations for the gas total temperature and total pressure at the anode nozzle exit when applied to the standard constant area heat addition equations. The investigation was carried out for anode nozzles of different lengths and led to the fact that nozzle length was not a great contributor to these losses for relatively short nozzles (1.25 to 2.00 in.). Nozzle length was also found to play a very minor role in relation to the other contributing factors in determining the efficiency of the arc-heating process. The arc-jet was operated with gas flow rates of approximately 0.0034, 0.0042, and 0.005 lb/ sec, electrical power input levels ranging from 2.7 to 5.8 kw, chamber pressures ranging from 6.7 to 11.7 psia, and gas inlet temperatures of approximately 530R.

Investigation of relation of pressure exerted by saturated soil to retaining wall displacement

Abstract: 1. The total pressure exerted by saturated soil is the sum of the respective pressures caused by the water and the buoyant soil. The fundamental laws for the pressure exerted by dry sand intrinsically apply also to sand located in a water environment. 2. Measured soil pressure on a rigid wall exceeds the active pressure by 30%. The distribution of soil pressure with respect to depth below wall crest, under active-pressure conditions, is not triangular but, rather, closer to a parabolic curve. 3. The point of application of the resultant pressure is definitely dependent on wall displacement, its position rising with total applied movement of the wall. 4. The relative wall displacement Δ/H cannot serve as a criterion for determining various parameters of soil pressure on the wall, inasmuch as they depend on specific soil properties, magnitude of soil friction against the wall, soil compressibility, etc. 5. In design the adoption of a uniform (rectangular) distribution of the supplementary pressure due to surcharge loading on the backfill surface is justified only in the case of smooth walls. Actually, the subject supplementary pressure diminishes with depth below backfill surface, and varies with wall roughness, soil properties, and the specific kinematic system for effecting wall displacements.

Investigation of an Actively Cooled Leading Edge for

Abstract: This report examines the engineering problems associated with the design of a water-cooled, tubular nickel leading edge for a hypersonic inlet. Small leading-edge radii (0.015-0.035 in.) were considered in order to minimize the distortion to the inlet flowfield. A design analysis was performed for conditions which could be obtained in the Applied Physics Laboratory (APL) arc-driven wind tunnel, viz., Mach 6.5, total temperature 5400°R, total pressure, 450 psia. Experiments on an 0.0255-in.-radius leading edge at these conditions showed that the integrity of the tube could be maintained even though the tube was deformed by small particles in the stream. Using moderate coolant velocities the calculated outer wall temperature at the stagnation point was 800°R, and the combined thermal and pressure stresses were found to be 24% of the elastic limit. Selected results of a more generalized study of the application of actively cooled leading edges for hypersonic vehicles are also discussed. The fabrication techniques used to join nickel tubes with electrodeposited nickel and to form a composite leading-edge structure for a second series of tests are described. Photomicrographs show that a bond of one-grain-bou ndary thickness can be achieved. Both single-tube and composite structures were tested at Mach 3.13 with stagnation conditions of 4440°R and 435 psia, giving 2.1 times the heating rate at the stagnation point attained with the Mach 6.5 tests. Assuming Newtonian flow and the Detra and Hidalgo correlation modified for a cylinder in cross flow, the estimated heat transfer to the leading edge was found to be 73% of the measured value.

Diffusive and convective flow in a hydrogen-atom flow system

Abstract: Diffusive and convective flow was studied in a hydrogen-atom flow system using an isothermal calorimetric detector. By varying detector area, total pressure, and linear flow rate, the importance of...

Correlations of turbine blade total-pressure- loss coefficients derived from achievable stage efficiency data.

Abstract: Smith correlation of turbine stage efficiency for relating achievable efficiency to stage loading and flow factors used for total pressure loss coefficient data