Showing papers on "Total pressure published in 1976"

Oxidation of Si3N4 in the Range 1300° to 1500°C

Abstract: The isothermal oxidation behavior of commercial hot-pressed Si3N4 was evaluated for temperatures from 1300° to 1500°C Multiphase scales were formed, consisting mainly of α-cristobalite and enstatite A large increase in reaction rate above 1450°C is believed to be caused by melting in the scale and the consequent increase in the rate of oxygen transport No oxygen pressure dependence was observed at 1400°C over the oxygen pressure range 10-9 atm to 600 torr However, a small decrease in the kinetics was observed when measurements were made in reduced total pressures of oxygen as compared to O2/N2mixtures at a constant total pressure

Xenon fluoride laser excitation by transverse electric discharge

Abstract: Stimulated emission has been produced in mixtures of He, NF3, and Xe at total pressures between 300 and 1000 Torr. Laser emission was on lines at 3511 and 3531 A which have been associated with the excited XeF molecule. Excitation of the gas mixture was by a transverse electric discharge which produced pulses with peak currents of approximately 104 A and rise times of 20 ns. A maximum laser energy of 7 mJ was obtained from a gas mixture with a ratio of He:Xe:NF3 of 98.0:1.5:0.5 at a total pressure of 300 Torr.

Ejector performance at high temperatures and pressures

Abstract: Attention has recently been given to the use of thrust augmenting ejectors in the wings of V/STOL aircraft. Laboratory experiments using low temperature and pressure primary air have measured high-performance levels with well-designed ejectors. The present experiments were motivated by aircraft designers' questions regarding the effects of realistic temperatures and pressures on ejector performance. The simplest geometry was used: a convergent nozzle issuing into an axisymmetric duct that entrained from and exhausted to ambient conditions. The length of the ejector was varied from 12 to 0.75 diam. Primary temperatures and pressures spanned the intervals 60 to 1000°F and 10 to 80 psig. In support of existing theory, the mass entrainment performance usually decreased with increasing primary pressure although an aeroacoustic interaction reversed the trend over small intervals. Increasing the primary temperature decreased the performance of long ejectors but had little effect on the performance of short ejectors. The results are interpreted in terms of measurements of the pressure along the wall of the mixing duct and total pressure and temperature profiles acquired at the exhaust plane of the ejector.

Intake control for air utilizing aircraft engines

Abstract: An air intake control for an air utilizing jet aircraft engine. The control is provided with fixed and movable air intake control ramps and the positioning of such movable ramps for air control purposes is determined by the static pressure above one thereof modified by the static pressure of the external air flow, the total pressure and the angle of attack of the aircraft. One control parameter is produced by a device responsive to the relationship between the static pressure above the one movable ramp and the total pressure of the external air flow. Particularly, this pressure relationship is calculated as a function of the operating cylinder feedback signal indicating the actual position of the center ramp, and is applied as a modifying value to a summing junction provided in the control circuit to produce a variable demand signal. The variable demand signal so generated is then compared with a signal representing a corresponding actual pressure relationship and the error signal, if any, so generated effects a corrective movement of the movable ramps until the error signal becomes zero.

Analytical Procedure for Calculation of Attached and Separated Subsonic Diffuser Flows

Abstract: An analytical procedure for computing the static and total pressure distributions in subsonic diffusers with axisymmetric or two-dimension al cross sections is described. It includes velocity profile and shear stress parameters which apply to attached and separated flows and allows for a strong interaction between the inviscid and viscous portions of the duct flow. With this approach, solutions can be obtained for separated regions where conventional boundary-layer methods fail. Analytical and experimental static and total pressure distributions are compared for plane-wall and conical diffusers. An approximate technique is used to apply the analysis to actual aircraft diffusers. A Ae a0 al9...,a7 blfb2,b3 CD D d

Device for dispersing gas into a liquid

Abstract: In a device for dispersing gas, e.g., air into a liquid or slurry in motion, wherein the surface at which dispersing takes place has a vertical extension and thus is subjected to varying hydrostatic pressure effected by the liquid or slurry, dispersing is optimized and the performance essentially improved by compensating the varying hydrostatic pressure with a dynamic pressure caused by the liquid in motion and varying in a desired manner so that the total pressure at least at most of the dispersing surface is substantially equalized. Said compensating is effected by providing for the correct flow rate and corresponding shape of the dispersing surfaces and other possible members influencing the liquid flow. In one embodiment the dispersing surface is represented by the envelope surface of a rotor rotating about a vertical axis.

Method for reducing the temperature of bakery products

Abstract: The temperature of bakery products is reduced immediately after the discharge thereof from the oven, by means of vacuum, by first subjecting the bakery products to a substantially linear pressure reduction as a function of time at a rate of not more than 60 mm Hg per second through at least half of the total pressure drop to be achieved. The pressure reduction rate is then allowed to increase substantially for a terminating vacuum treatment. At least one vacuum chamber is provided and is adapted to be connected to a source of vacuum through a vacuum conduit and a valve, and has a closeable opening for bringing bakery products into and out of the chamber. In the vacuum conduit, in parallel to a servo-valve serving to apply a full vacuum effect from the source of vacuum during the remaining portion of the total pressure drop, there is inserted a by-pass conduit having a permanently open cross-section which can be adjusted to provide the substantially linear pressure reduction.

Blade row dynamic digital compressor program. Volume 1: J85 clean inlet flow and parallel compressor models

Abstract: The results are presented of a one-dimensional dynamic digital blade row compressor model study of a J85-13 engine operating with uniform and with circumferentially distorted inlet flow. Details of the geometry and the derived blade row characteristics used to simulate the clean inlet performance are given. A stability criterion based upon the self developing unsteady internal flows near surge provided an accurate determination of the clean inlet surge line. The basic model was modified to include an arbitrary extent multi-sector parallel compressor configuration for investigating 180 deg 1/rev total pressure, total temperature, and combined total pressure and total temperature distortions. The combined distortions included opposed, coincident, and 90 deg overlapped patterns. The predicted losses in surge pressure ratio matched the measured data trends at all speeds and gave accurate predictions at high corrected speeds where the slope of the speed lines approached the vertical.

Investigation of minimum operating temperatures for cryogenic wind tunnels

Abstract: Total temperatures corresponding to the onset of condensation effects were determined for flow over a 0.137-m NACA 0012-64 airfoil mounted in the Langley 1/3-m transonic wind tunnel. Tests were carried out at a total pressure range from 1.2 to 4.5 atm and at free-stream Mach numbers of 0.75, 0.85, and 0.95. No condensation effects were found to occur until total temperatures were below those associated with free-stream saturation. Significant increases in Reynolds number may apparently be obtained by operation at wind tunnel temperatures below those associated with local saturation over the airfoil but above those where effects first occur. For the 0.85 and 0.95 Mach numbers the increase in Reynolds number was at least 15% over those achieved at local saturation conditions for the same pressure range. Higher pressures may have had some detrimental effect in the 0.95 Mach number test.

Optical gain in a neutron‐induced 3He‐Ne‐O2 plasma

Abstract: A single pass gain of ∼0.9% p/m (at 8446 A in atomic oxygen) has been measured for a 3He‐Ne‐O2 plasma generated by the volumetric 3He(n,p)3H reaction induced by neutrons from a pulsed nuclear reactor. The plasma was contained in an optical cavity containing a chopping fan that permitted a measurement of the ratio of output 8446 A from the normal cavity to that with the back mirror blocked. This ratio, called the unblocked‐blocked ratio, was used to study the gain dependence on total pressure and concentration. The maximum gain observed was for a concentration of 0.048% O2 and 1.5% Ne, at a total pressure of 600 Torr. The peak gain remained fairly constant with neutron fluxes from 1013 to 2.5×1015 n/cm2 sec. Results of other concentration studies are also discussed. The laser medium is pumped by thermal neutrons from the Illinois TRIGA reactor that impinge on a 80‐cm by 0.8‐cm‐i.d. glass tube containing from 50 to 800 Torr 3He‐Ne‐O2.

An Experimental and Analytical Investigation of Axisymmetric Diffusers

Abstract: A finite difference computer program for turbulent compressible flow was used to establish the performance of several diffuser shapes for experimental testing. The diffusers were designed to have a linear change in Mach number, a linear change in pressure, or a curvature fitted by a quadratic equation. Testing was performed with M = 0.1 to 0.9 with and without boundary layer bleed. Above M = 0.6, data were obtained with a normal shock upstream of the diffuser entrance. Peak static pressure recovery occurred with a diffuser inlet M0.75. The quadratic diffuser yielded the highest total pressure recovery.

Method and a device for detecting the stall condition of an axial flow fan or compressor

Abstract: The stall condition occurring in the unstable working range of an axial flow fan or compressor arranged in an air duct is detected by measuring the pressure difference between the total air pressure acting in a direction opposite to the direction of revolution of the fan wheel and a reference pressure corresponding substantially to the static pressure at the wall of the air duct in the same radial measuring plane. The detector device comprises first and second pressure measuring probes of an open tubular configuration for measuring said total pressure and reference pressure, respectively, and means for detecting the difference between the pressure values measured thereby, said probes being designed and arranged in the air duct so that the flow conditions around them are equal in the stable working range of the fan or compressor.

Methods and apparatus for determining total flow rate of gaseous fluids

Abstract: Methods and apparatus for determining the total flow rate of gaseous fluid passing through a plurality of conduits utilizing a plurality of total and static pressure sensing probes, the number of total pressure sensing probes being selected and deployed within each conduit to cover cross-sectional areas of substantially equal and corresponding size, each total pressure sensing probe being connected to one central pressure averaging manifold and each static sensing probe being connected to a second pressure averaging manifold, the pressure difference between the two pressure averaging manifolds being compared to determine the pressure difference as a measure of average velocity. In addition, the fluid flow to and from each manifold is controlled, as by means of a restriction, to impede the flow while providing a substantially laminar flow and a Reynolds number less than 4,000.

Experimental evaluation of premixing-prevaporizing fuel injection concepts for a gas turbine catalytic combustor

Abstract: Experiments were performed to evolve and evaluate a premixing-prevaporizing fuel system to be used with a catalytic combustor for possible application in an automotive gas turbine. Spatial fuel distribution and degree of vaporization were measured using Jet A fuel. Three types of air blast injectors, an air assist nozzle and a simplex pressure atomizer were tested. Air swirlers with vane angles up to 30 deg were used to improve the spatial fuel distribution. The work was done in a 12-cm (4.75-in.) diameter tubular rig. Test conditions were: a pressure of 0.3 and 0.5 MPa (3 and 5 atm), inlet air temperatures up to 800 K (980 F), velocity of 20 m/sec (66 ft/sec) and fuel-air ratios of 0.01 and 0.025. Uniform spatial fuel distributions that were within plus or minus 10 percent of the mean were obtained. Complete vaporization of the fuel was achieved with air blast configurations at inlet air temperatures of 550 K (530 F) and higher. The total pressure loss was less than 0.5 percent for configurations without air swirlers and less than 1 percent for configurations with a 30 deg vane angle air swirler.

Effect of inlet temperature and pressure on emissions from a premixing gas turbine primary zone combustor

Abstract: Experiments were conducted to determine the performance of a premixing prevaporizing gas turbine primary zone combustor design over a range of combustor inlet temperatures from 700 to 1000 K and a range of inlet pressures from 40 to 240 N/sq cm. The 1 meter long combustor could be operated at pressures up to and including 120 N/sq cm without autoignition in the premixing duct or flashback from the stabilized combustion zone. Autoignition occurred in the mixer tube at the 240 N/sq cm pressure level with an entrance temperature of 830 K and a mixer residence time of 4 msec. Measured NOx level, combustion inefficiency, and hydrocarbon emission index correlated well with adiabatic flame temperature. The NOx levels varied from approximately 0.2 to 2.0 g NO2/kg fuel at combustion inefficiencies from 4 to 0.04 percent, depending upon adiabatic flame temperature and pressure. Measured NOx levels were sensitive to pressure. Tests were made at equivalence ratios ranging from 0.35 to 0.65. The overall total pressure drop for the configuration varied slightly with reference velocity and equivalence ratio, but never exceeded 3 percent.

Pressure and velocity in a developing coaxial jet

Abstract: Determinations of static pressure, mean velocity and turbulence intensity in the developing region of coaxial jets are presented. Detailed profiles were obtained at twelve axial locations (extending from the nozzle exit for a distance of 5 diameters) downstream from a single element of the Bell Aerospace H2/O2 19-element coaxial injector. Measurements of mass-flux per unit area (using a constant temperature anemometer), total pressure and local temperature were used in the determination of local static pressure and velocity. These data show a low pressure region exists near the nozzle exit. Although this pressure reduction is small (0.34 psi), it substantially altered the flow development. Comparison of results shows that velocity near the nozzle exit decreases initially (no central velocity core) as a result of both pressure gradients and viscous mixing. These data are compared with analytical predictions made using available computer codes. Results show the need to consider pressure effects in any proposed mathematical model.

Calculation of the Turning Angle of Two-Dimensional Incompressible Cascade Flow

Abstract: Nomenclature t — tangential spacing between blades / = chord length X = staggering angle (0 for unstaggered cascades, A + /37 + a5 = 90°) Wj = inlet velocity j87 = inlet angle as = angle of attack (angle between inlet velocity and chord) w2 = outlet velocity of real flow = outlet angle of real flow — j31 = turning angle (xu/l)s = distance between leading edge and transition point on the upper surface, measured on chord, referred to chord length 1 CD =drag coefficient (total drag, referred to upstream dynamic pressure and chord length) A/3; = correction value for inlet angle, inserted into calculation S = pressure coefficient (difference between up-stream total pressure and local pressure on blade surface, referred to up-stream dynamic pressure) x/l = distance between control-point and leading edge, measured on chord, referred to chord length d/l = ratio of maximum thickness and chord length Re = Wj»l/v = Reynolds number v = kinematic viscosity

A method of distortion pattern synthesis for high response data screening

Abstract: An empirically derived method of estimating maximum levels of instantaneous inlet total pressure distortion from steady state measurements is presented. The estimation procedure uses steady state total pressure and root mean square turbulent pressure data measurements to synthesize instantaneous distortion patterns. The synthesis method is tailored to intensify distortion patterns in a manner consistent with the characteristics of the particular index to be used in evaluating inlet/engine compatability. The maximum expected value of distortion, a statistically determined function of the length of time of inlet operation, is used to constrain the amount of pattern intensification. Comparison with an independent set of data is presented for verification of the synthesis method.