Showing papers on "Total pressure published in 1971"

Oxidation/Vaporization Kinetics of Cr2O3

Abstract: The weight loss of Cr2O3 in oxidizing environments (Po2= 1 to 10−3 atm) at 1200°C was measured. Both hot-pressed and sintered Cr2O3 pellets were investigated in O2/Ar gas mixtures, and the dependence of the weight loss on the O2 partial pressure, the gas flow rate, and the total pressure was determined independently. The experimentally determined O2 partial pressure dependence (rate ∝ PO23/4) corresponds to that expected for the reaction Cr2O3(s)+3/2O2⇌2CrO3(g). The flow rate and total pressure dependencies show that mass transport through a gaseous boundary layer is the rate-controlling step in the oxidation/vaporization of Cr2O3. Evaporation coefficients for the loss of CrO3(g) under the experimental conditions were <0.01.

Measurements of the curves-of-growth of hot water vapor

Abstract: The curves-of-growth of water vapor were measured in the temperature range from 1000 K to 3000 K at a total pressure of 1 atm with a strip burner 6 m long. The fuel was gaseous hydrogen and oxygen. The statistical band model with exponential line intensity distribution was used to reduce the experimental data to yield spectral absorption coefficients (line strength/line spacing) and fine structure parameters (line width/line spacing), averaged over 25-cm−1 spectral intervals, in the region from 1 μ to 10 μ. Because of the fuels used, the foreign gas broadener was oxygen. An expression is given which permits the calculation of the spectral emission as a function of total pressure, partial pressure of water vapor, and foreign gases and path length. The range of total pressures is limited to the region in which collision broadening is predominant (~0.1 atm to several atm). The results are compared with previous results and with independent laboratory studies. The agreement is excellent.

Heat Pipe Oven Applications. I. Isothermal Heater of Well Defined Temperature. II. Production of Metal Vapor‐Gas Mixtures

Abstract: A concentric heat pipe oven is described, which serves as an oven with a highly homogeneous temperature distribution as required by such applications as crystal growing, thermal treatment of materials, and radiation standards. The design is simpler than conventional ovens with similar temperature stability and homogeneity. The temperature control is replaced by a pressure control. This device is used in a modification of the heat pipe oven that generates homogeneous mixtures of a vapor (such as a metal vapor) and an inert gas at well defined total pressure, partial pressure, temperature, and optical path length. All the features of the previously described heat pipe oven are maintained with the additional option that allows quantitative total and partial pressure measurements without relying on vapor pressure curves.

Temperature and Pressure Effects in the Addition of H Atoms to Propylene

Abstract: The effect of He pressure on the rate of addition of hydrogen atoms to propylene was measured at 298°K. H‐atom concentration was measured by the method of resonance fluorescence of Lyman α radiation at 121.6 nm. The results are consistent with the 1 / p1/2 dependence of kbi recently observed in the H‐atom–ethylene system. The limiting high‐pressure rate constant obtained in this work is H+C3H6→C3H7, k1 = 1.61 ± 0.04 × 10−12cm3molecule−1·sec−1. The temperature dependence of the H‐atom addition was investigated at 50 torr total pressure over the temperature range 177–473°K. Analysis of the data below room temperature gives the following Arrhenius parameters for addition to the terminal olefinic position: kbi50 = (10.18 ± 0.26) × 10−12exp[− (1211 ± 11) / 1.987T] cm3molecule−1·sec−1. Deviations from this dependence above 298°K can be assigned to nonterminal addition, H‐atom abstraction, and increased decomposition of the excited propyl radicals.

Entrance‐ and Exit‐Correction in Capillary Flow of Molten Polymers

Abstract: An apparatus is designed for the determination of the axial pressure distributions of molten polyethylene and polypropylene, both in a capillary and in a reservoir. Experimental results reveal that the pressure at the tube exit, termed “exit pressure,” is above atmospheric and it is found to be shear dependent for a given L/D ratio. The authors suggest a modified Bagley plot corrected for “exit pressure.” Such plots show curvature at the entrance region. The plots of entrance‐correction vs. wall shear stress also show curvature, thus indicating that Hooke's law in shear is not obeyed by the polymers under study. The “exit pressure” is further used to correlate with the total pressure drop at the entry to the tube.

Fan capacity measuring station

Abstract: A fan capacity measuring station wherein the fan discharge is first conditioned for accurate flow rate measurement by fixed mixing vanes that break up stratification and negative pressure pockets and by subsequent straightening means that eliminate turbulence and produce substantially laminar air flow through a measuring section of known cross-sectional area. Then in the measuring section total pressure sensors, manifolded in a traverse, average the total pressure and manifolded static pressure sensors average the static pressure. The difference between the average total and static pressure of the conditioned discharge is a direct and accurate measurement of flow rate within + OR - 1 percent.

Effect of inlet geometry on flow-angle characteristics of miniature total-pressure tubes

Abstract: Inlet nozzle geometry effects on subsonic flow characteristics of miniature total pressure tubes including pitot tube static and dynamic pressure and flow velocity measurements

Pyroxmangite: Stability in H2O-CO2 mixtures at a total pressure of 2000 bars

Abstract: The curve of the reaction: 1 Rhodochrosite + 1 Quartz ⇌ Pyroxmangite was determined experimentally using gas mixtures with different CO2H2O ratios at a total pressure of 2 kb. In pure CO2, the equilibrium temperature is 508±2° C. By plotting the equilibrium data in terms of InXCO2 versus reciprocal temperature, a ΔH of reaction of 51.7 kcal was obtained. This plot shows a straight-line relationship, indicating internal consistency of the data, and is in good agreement with previous findings that CO2 and H2O mix ideally within the investigated temperature range (400–600° C). When applied to pyroxmangites formed during moderate greenschist facies metamorphism, these data indicate a high acitivity of H2O.

Effects of Engine Exhaust Flow on Boattail Drag

Abstract: Wind-tunnel tests were conducted to investigate the effects of jet plume shape and entrainment on hoattail pressure drag. The results were used to determine nozzle drag levels at various engine operating conditions as well as at conditions related to airplane force models. An isolated nozzle model with a pressure-tapped exterior and changeable internal parts was tested subsonically to examine changes in drag due to alterations in internal geometry and nozzle pressure ratio. In addition, tests were run with solid plume-shaped sleeves as a means to separate plume-shape effects from jet entrainment effects. Large differences in drag were measured with changes in plume shape, and, in certain regimes, jet entrainment also had a significant effect. The results of this study include boattail pressure distributions, integrated drag coefficients, and a comparison of test data with analytically predicted drag levels. Nom enclatur e A = cross-sectional area CD = boattail pressure drag coefficient (drag/g<^4.m) Cp = boattail pressure coefficient [(P — Po)/qQ] D,d = diameter h = boundary-layer height L = length of boattail MQ = freestream Mach number NPR = nozzle pressure ratio (PTJ/PO) P = local static pressure Po = freestream static pressure PTJ = exhaust jet total pressure q = dynamic pressure R = radius /3 = boattail trailing-edge angle Subscripts boattail terminal plane jet B,b J M,m T maximum freestream total

Oxidation-Reduction Kinetics in MnO

Abstract: The oxidation-reduction kinetics of MnO in CO/CO2 atmospheres at 1230°C were measured by gravimetric and electrical conductivity techniques. The dependence of the kinetics on time, inert gas dilution, total pressure, and specimen thickness indicates that the kinetics are controlled by a slow surface reaction step. Attempts to analyze the data quantitatively using equations for linear heat flow in a solid with a radiation boundary condition were unsuccessful.

Determination of Vapor-Liquid Equilibrium from Total Pressure Measurement

Abstract: The total pressure of a solution of known composition was measured by using a new experimental method for the binary mixtures of C3-hydrocarbons and solvents. From these measurements the vapor compositions were calculated by Barker's method. Preliminarily, the method was applied to some binary systems of high relative volatility covered pressures up to 30atm. The predicted vapor compositions give a sufficient representation of the data.

Mechanisms of ignition of thermally irradiated cellulose

Abstract: The experimentally determined dependence of spontaneous ignition of radiantly heated cellulose on atmospheric variables is presented and compared with calculated responses based on an idealized model of thermal autoignition in the gas phase. The atmospheric variables are: total pressure (subatmospheric to 4 atm), oxygen concentration (pure diluent to pure oxygen), and diluent replacement (helium and carbon dioxide substituted for nitrogen). As both total pressure and oxygen concentration are increased from their ignition-limiting values (e.g., air at 0.15 atm pressure and 16% oxygen in nitrogen-oxygen mixtures at 1 atm), the times required for ignition fall monotonically from large values (relative to ignition time in air) to values that are substantially less than ignition times in air. The effect of diluent changes is similarly profound. These data render untenable previously reported speculation regarding initiation by the sudden appearance of active species among the pyrolysis products. They are shown to be consistent with the classical processes of thermal autoignition. A simplified model incorporating these processes has been developed. Details of the model and results obtained with it are reported.

Incompressible, viscous, swirling flow through a nozzle

Abstract: The viscous core of an incompressible, swirling flow through the nozzle is treated by momentum-integral equations. These equations, together with the statement of the conservation of mass in the whole nozzle and the conservation of momentum along the nozzle axis, form a system of four ordinary, nonlinear differential equations. This system of equations is solved for the circumferential and axial velocities both inside and outside the core. This system has a singularity which occurs when the square of the ratio of the circumferential to axial velocities, at core boundary, reaches a certain value depending upon the axial velocity profile. This singularity divides the possible solutions into those in which the core is massflow dominated and those in which the core is swirl dominated. The massflow-dominated core occurs at low swirl and is characterized by high discharge coefficient, which is essentially unaffected by the swirl and by a certain maximum total pressure loss which is inversely dependent on nozzle contraction. The flows with the swirl-dominated core have their discharge strongly throttled by the swirl, have the capability to sustain very large total pressure loss, and usually have regions of reversed axial velocity. The increase of Reynolds number tends to decrease the discharge coefficient, whereas the change from laminar to turbulent flow tends to increase the discharge coefficient. Both of these effects are particularly pronounced in swirl-dominated flows.

The pressure distribution in axisymmetric draining films

Abstract: The variation in excess, flow, and total pressure within axisymmetric draining films beneath liquid drops and rigid spheres, approaching plane and deformable interfaces, has been obtained from experimental and theoretical variations in film thickness with time and position. Such pressure distributions slowly approach those within an equilibrium films of zero thickness inwhich drainage has ceased. The pressure is always close to the equilibrium variation near the center of the film but some deviation occurs towards the periphery of the film.

Experimental investigation of the effect of screen induced total pressure distortion on turbojet stall margin

Abstract: Effect of circumferential, radial, and combined pressure distortions on stall margin of J-85 engine

Influence of surface roughness on the flow through a staggered tube bank

Abstract: The influence of surface roughness on the cross-flow through a staggered tube bank is investigated in the range of Reynolds numbers 4 ×104

Device for locating a film transparency

Abstract: A device for locating a film transparency along the light path of a projector having an optical axis includes a bracket for holding a transparency in the projector for movement along the optical axis from a reference plane intersecting the light path. Means are provided for directing a current of air against the one surface of the transparency to form a first region on that surface wherein the pressure exerted on the transparency is greater than atmospheric pressure and a second region wherein the pressure exerted on the transparency is less than atmospheric pressure. The opposite surface of the transparency is exposed to atmospheric pressure. The transparency will be moved by the pressure imbalance until the total pressure exerted on the one surface is equal to the atmospheric pressure exerted against the opposite surface.

Fuel control for turbine type power plant having variable area geometry

Abstract: The turbine inlet temperature of a turbine type of power plant, particularly the type that includes a variable geometry, is controlled by setting a referred weight flow of the power plant working medium and closing the loop through fuel flow so that the actual referred weight flow matches the set value. The ratio of the difference between the total pressure upstream of the burner and the static pressure downstream of the burner to the total pressure upstream of the burner serves to produce a signal indicative of the actual weight flow of the power plant working medium.

On the cross flow through in-line tube banks with regard to the effect of surface roughness

Abstract: The behaviour of the flow through an in-line tube bank is studied at variable roughness conditions of the surface. The total pressure loss, the local static pressure and the skin friction distribution were measured in the range of Reynolds numbers 4·104

Wind Tunnel Testing of Interactions of High Altitude Rocket Plumes with the Free Stream

Abstract: : Interactions of model rocket plumes and the free stream at varying simulated altitudes have been investigated in an altitude simulation chamber. Free-stream variables were Mach number, gas, total temperature, and total pressure. Model rocket parameter variables were exhaust gas, area ratio, chamber total pressure and total temperature, and the orientation of the model relative to the free stream. In addition to pitot probe measurements, plume photographs and density measurements were obtained using the electron beam technique.

Flow sonde for measuring the total pressure and the static pressure of a flow

Abstract: This invention relates to a flow sonde for measuring the total pressure and the static pressure of a flow comprising a cylindrical forward section, a conical transitional section, a rearward cylindrical section, said forward section having a smaller diameter than said rearward section and the transitions from each section to the next extending in a sharp-edged manner, and aperture means on said sonde for taking the total pressure and the static pressure.

High Temperature Thermal Decomposition of Carbonyl Fluoride

Abstract: The thermal decomposition of carbonyl fluorine (COF2) in excess argon, , was studied behind both incident and reflected shock waves. Kinetic data were obtained in the temperature and total piessure ranges 2600-3600°K and 0.5 to 12 atmospheres respectively. The reaction was found to be unimolecular in nature, and the variation of the observed rate constant with temperature and total pressure was analyzed with the aid of both the Lindemann and the Rice-Ramsperger-Kassel unimolecular theories of reaction rates. The experimentally determined activation energy for the high pressure limiting rate constant is shown to be slightly in excess of the first bond dissociation energy of COF2, and the Lindemann theory is shown to best fit the experimental data. The results of previous investigators are compared to the findings reported here, and the sensitivity of the reaction rate to trace water vapor impurities is discussed.

Low-Pressure Oxidation of Cb–1Zr Alloy

Abstract: Resistively heated strip specimens of Cb-1Zr alloy were exposed at 927 °C in a vacuum chamber at various levels of total pressure in the 10−6-Torr range and oxygen partial pressures in the 10−7-Torr range. Pressure levels were maintained by controlled in-leakage of air. Oxygen reacts rapidly with Cb–1Zr alloy under these conditions and final oxygen content of the specimens was between 4000 and 9000 ppm for exposure times between 200 and 500 h. Oxygen reaction rates (sticking probabilities) were calculated both from the total oxygen pickup and from the vacuum chamber gas analyses. Good agreement was obtained between the two methods. Oxygen sticking probabilities were found to depend on whether or not the specimens were annealed immediately before the test exposure. These results indicate that a normally undetectable oxide film exists on the Cb–1Zr surface as a result of oxidation by ambient air, and causes the sticking probability to be lower than on the clean metal surface. Sticking probabilities ranged f...

The Design of an Axial Compressor Stage for a Total Pressure Ratio of 3 to 1

Abstract: : The report describes in detail the aerodynamic design of a supersonic axial compressor stage The principal design-point characteristics of the stage are a corrected tip speed of 1600 ft/sec, an inlet hub/tip radius ratio of 075, a total pressure ratio of 30, and an isentropic efficiency of 82% Four features distinguish this stage from other reported stages A new type of rotor airfoil is employed The stator leading edges are swept back from both walls toward mid-passage Unusually large and variable fillet radii blend blades with platforms Also, a new and precise technique was used to determine Cartesian manufacturing coordinates for the airfoils, aerodynamically defined on streamsurfaces The preliminary design employed a technique resulting in equilibrium radial distributions of loss coefficient and flow angle which are fully consistent with relative Mach numbers and diffusion factors for each blade row and on each streamsurface according to a prescribed loss model The detail design was accomplished using computing stations internal as well as external to both blade rows and attempted to optimize the axial distribution of static pressure