Showing papers on "Total pressure published in 1970"
TL;DR: In this paper, the authors studied the hydrogen atom-ethylene system at 298°K employing the methods of resonance fluorescence and absorption by hydrogen atoms of Lyman α radiation at 1216 A. Their results indicate that stoichiometric factors obtained under low-pressure conditions may not be applicable to high pressure.
Abstract: The hydrogen atom–ethylene system was studied at 298°K employing the methods of resonance fluorescence and absorption by hydrogen atoms of Lyman α radiation at 1216 A. The contribution of hydrogen atom–radical reactions was evaluated under varying experimental conditions, and the rate of disappearance of H atoms in ethylene was measured under conditions where stoichiometric corrections became significant. Measurements in the literature of reaction rates for H+C2H4 at low total pressure are now in good agreement; however the limiting high‐pressure absolute rate constants thus far reported differ depending on the assignment of stoichiometric factors. Our results indicate that stoichiometric factors obtained under low‐pressure conditions may not be applicable to high pressure. Furthermore, extrapolations based on plots of inverse rate constant vs inverse pressure may be in error due to significant curvature in such plots. Our high‐pressure limiting rate constant for H+C2H4, extrapolated from data at pressure...
78 citations
TL;DR: In this article, the transpiration method was used with flowing H2-H2O mixtures in order to fix the oxygen potential of the carrier gases, and therefore, the composition of the condensed phase.
56 citations
TL;DR: Isothermal vapor-liquid equilibrium data were obtained by the total pressure method for the binary systems acetaldehyde-ethanol, acetaldehyde -water, and ethanol-water at 10°, 15°, 20°, 25°, and 30°C, using a modified Menzies and Smith's isoteniscope.
Abstract: Isothermal vapor-liquid equilibrium data were obtained by the total pressure method for the binary systems acetaldehyde-ethanol, acetaldehyde-water, and ethanol-water at 10°, 15°, 20°, 25°, and 30°C, using a modified Menzies and Smith's isoteniscope. Barker's method was employed for the numerical calculations.
47 citations
TL;DR: The X-type pseudo-shock was investigated in this article, which appeared at comparatively high Mach number, and was compared with the λ-type Pseudo-Shaking reported in the previous paper.
Abstract: The X-type pseudo-shock was investigated, which appeared at comparatively high Mach number, and was compared with the λ-type pseudo-shock reported in the previous paper. The similarity and difference between them were discussed. At the duct center, the shock loss by the leading shock wave is smaller for the X-type pseudo-shock than for the λ-type one, but near the wall and in the subsonic region, the flow conditions are similar. The over-all total pressure loss is affected by the mixing of the flow near the wall with the main stream and the so-called shock loss is rather small. the effect of the boundary layer and the wall friction force on the static pressure rise of the pseudo-shock is also made clear. The simple model for the mechanism of the pseudo-shock is presented in the appendix.
38 citations
TL;DR: In this article, the authors measured flow and pressure maldistributions at the distributor level of a 4 ft × 4 ft bed of silica sand, fluidised by both uniform and non uniform distributors, over a wide range of bed depth, superficial velocity and distributor pressure drop.
27 citations
TL;DR: The electron impact desorption (E.I.D) effect can cause significant errors in total pressure measurement with hot-cathode gauges and can change the striking characteristics of magnetic, cold-cadave gauges.
Abstract: When electrons strike certain adsorbed gases, positive ions, neutrals, and/or excited neutrals are released. This electron impact desorption (E.I.D.) effect can cause significant errors in total pressure measurement with hot-cathode gauges and can change the striking characteristics of magnetic, cold-cathode gauges. In certain mass spectrometers, “surface ion” peaks appear in the mass spectrum resulting from E.I.D. of gases sorbed at the ion source electrodes. The general characteristics of E.I.D. and the results of measurements of E.I.D. from metal surfaces are briefly reviewed. The effects of E.I.D. on the characteristics of hot- and cold-cathode gauges and mass spectrometers are considered in some detail. Methods of minimizing errors caused by E.I.D. are discussed.
27 citations
TL;DR: The diffusion coefficients of oxygen in single crystals of nickel ferrite with Fe/Ni=3.4 were determined as a function of oxygen stoichiometry between 1140° and 1340°C as mentioned in this paper.
Abstract: The diffusion coefficients of oxygen in single crystals of nickel ferrite with Fe/Ni=3.4 were determined as a function of oxygen stoichiometry between 1140° and 1340°C. The diffusion kinetics were followed by measuring the rate of exchange of 18O between the gas and solid slabs of ferrite, and the oxygen stoichiometry was established by controlling total pressure of oxygen in the gas phase. At higher oxygen contents, the diffusion coefficient is independent of stoichiometry and is given by D=10-2.3exp cm2/s. At low oxygen contents the diffusion rate depends strongly on oxygen stoichiometry and is smaller. In polycrystalline ferrite the diffusion at 1197°C is 40 times faster than in single crystals but shows the same dependence on oxygen stoichiometry. Probable diffusion mechanisms are discussed.
25 citations
Patent•
13 Apr 1970
TL;DR: In this paper, an air monitoring system is provided for direct measurement of the volume of air flow, and its velocity and pressure in one or a composite of several air ducts.
Abstract: An air monitoring system is provided for direct measurement of the volume of air flow, and its velocity and pressure in one or a composite of several air ducts. The system includes flow measuring stations which are installed in each duct as a permanent part thereof. Air moving in the duct first passes through a flow straightening section in each station which comprises a honeycomb of short, axially extending passages. Movement of the air through the straightening section eliminates turbulence in the entering air and produces substantially laminar air flow. A plurality of total pressure sensors are positioned in one or more traverses across, immediately adjacent to, and downstream of the straightening section to sense the total pressure of the flowing air. The total pressure values sensed by the several sensors are averaged by a manifold which connects with each of them. The individual total pressure sensors are so distributed as to be at the center of cross-sectional segments of the duct having equal areas. Static pressure at each station is also sensed by static pressure sensing tips, averaged and used with the total pressure to determine air flow. A tube leading directly from a remotely located manometer is connected to the manifold of the total pressure sensors at a point symmetrically arranged with respect to the total pressure sensors.
24 citations
TL;DR: In this paper, experimental data on propagation characteristics of compression and rarefaction waves in steam-water mixtures are presented. And the front velocity of both types of waves are shown to be essentially the same and can be predicted if the flow regime is known.
16 citations
TL;DR: In this paper, the authors used an improved total pressure probe to measure the velocity of liquid in the presence of turbulence, and the results showed that the probe was effective in detecting the anomalous behavior of liquid.
Abstract: (1970). Turbulence Measurements In Liquids Using An Improved Total Pressure Probe. Journal of Hydraulic Research: Vol. 8, No. 2, pp. 131-158.
14 citations
19 Jan 1970
TL;DR: In this article, wind-tunnel tests were conducted to investigate the effects of jet plume shape and entrainment on hoattail pressure drag, and the results were used to determine nozzle drag levels at various engine operating conditions as well as at conditions related to airplane force models.
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
TL;DR: In this article, the equilibrium and free surface sublimation pressures of bismuth telluride were determined by the torsion−effusion and torsionslangmuir techniques, respectively.
Abstract: The equilibrium and free surface sublimation pressures of bismuth telluride were determined by the torsion‐effusion and torsion‐Langmuir techniques, respectively. Based on a least‐square fit, the expression for the equilibrium pressure in the temperature range of 722°–828°K was found to be: , where is the absolute temperature and the given uncertainties are the standard deviations. A similar treatment of the results of free surface pressure over basal plane oriented single crystals gave the following expression for the apparent total pressure in the temperature range of 741°–793°K: . Assuming the sublimation reaction , average third‐law enthalpies and activation enthalpies of sublimation at 298°K were found to be , respectively. Calculated values of the sublimation coefficient varied from 0.14 at 722°K to 0.39 at 828°K.
TL;DR: In this paper, a test program was performed using a 1.2 area ratio scale model nozzle to determine the nature of the flowfield, where secondary flows of 0 and 2% were introduced into the nozzle.
Abstract: Operation of a convergent-divergent (C-D) nozzle at low-pressure ratios can cause the internal flow to separate and possibly be unstable. A test program was performed using a 1.2 area ratio scale model nozzle to determine the nature of the flowfield. Secondary flows of 0 and 2% were introduced into the nozzle. Results of these tests are as follows: 1) High response pressure transducer readings internally along the nozzle lip provided no indication of a moving shock, either axially or circumferentially. Pressure fluctuations were greatest at a location near the point of separation. The maximum amplitude was small, 3.5% of the total pressure. 2) Hysteresis tests were run with the possibility of their uncovering a clue as to unstable separation in a more elastic model. No hysteresis was observed. 3) Secondary flows had little effect on the maximum amplitude of the pressure fluctuation. Its main influence was to move the shock system slightly upstream in the nozzle.
Patent•
27 Mar 1970
TL;DR: The helium content of a gaseous mixture is determined by comparing the partial pressure of the helium in an unknown sample directly with the pressure of highly purity helium under the same conditions as mentioned in this paper.
Abstract: The helium content of a gaseous mixture is determined by comparing the partial pressure of the helium in an unknown sample directly with the pressure of highly purity helium under the same conditions. The volume percent of helium in the unknown is equal to(P1/P2) X 100, where P1 is the partial pressure of helium in the sample and P2 is the total pressure of an equal volume of high-purity helium. The partial pressure of the helium in the unknown sample is initially determined by adsorption of gases other than helium on activated charcoal and measurement of the resulting helium pressure. The total pressure of high-purity helium is then measured under the same conditions as the sample.
TL;DR: In this paper, a simple 180°, miniature magnetic mass spectrometer was used to improve vacuum techniques on rotary pump, diffusion pump and ion pump systems operating from 10−3 torr to UHV.
01 Feb 1970
TL;DR: In this article, the influence of Mach number, total pressure, total temperature, and auxiliary plenum suction on the test section fluctuating pressures was evaluated in the AEDC PWT 16-ft transonic wind tunnel circuit.
Abstract: : An investigation was conducted to evaluate the fluctuating pressures in the AEDC PWT 16-ft transonic wind tunnel circuit. Test results were obtained over a Mach number range from 0.6 to 1.3 and a unit Reynolds number range from 1.8 to 6.8 million. The influence of Mach number, total pressure, total temperature, and (auxiliary) plenum suction on the test section fluctuating pressures was determined. In addition, a comparison of the Tunnel 16T fluctuating pressures with those of the AEDC PWT 4-ft transonic tunnel and the NASA-Huntsville 14-in. transonic tunnel is made. A critical Mach number range was defined near a Mach number of 0.75. The maximum root-mean-square fluctuating pressure in the test section was 3.5 percent of the free-stream dynamic pressure in the critical Mach number range. The source of this maximum fluctuating pressure did not appear to be controlled by the compressor. The free-stream fluctuating pressure was found to vary inversely with the total pressure and to be relatively invariant with total temperature and auxiliary plenum suction.
TL;DR: In this article, the orientation of excited19F nuclei following the reaction19F(α, α′) is studied in terms of the anisotropy of the delayed 197 keV-γ-radiation.
Abstract: Within a gaseous target of a mixture of SF6 and CH4 at a total pressure of 1 atm the orientation of excited19F nuclei following the reaction19F(α, α′) is studied in terms of the anisotropy of the delayed 197 keV-γ-radiation. By observing the nuclear Larmor precession differentially in time, this anisotropy is found (i) to be constant in time from 50 to 500 nsec after excitation, and (ii) to increase from zero to 60% of the anisotropy observed in a solid CaF2 target, if the relative CH4 concentration in the target gas of constant total pressure is varied from 0 to 90%. The attenuation of the anisotropy as compared to the value in CaF2 is explained by a strong perturbation of the nuclear alignment by statistical changes of the atomic fields at the end of the recoil stopping process. The observed partial conservation is interpreted as the contribution of those recoils which have become part of the stable diamagnetic HF molecules before being desoriented. A qualitative discussion shows that the nuclear alignment survives the recoil stopping process down to residual energies of less than a few eV.
01 Jan 1970
Patent•
10 Jun 1970
TL;DR: In this article, the shadow mask of a colour tube is replaced with an apertured metallic member such as the shadow-mask of a shadow mask in a color tube, such that the hydrogen is released first so that subsequent evaporation of the getter at a higher temperature secures a more uniform deposition on the metallic member and on adjacent parts of the envelope wall.
Abstract: 1,194,357. Cathode-ray tubes. SYLVANIA ELECTRIC PRODUCTS Inc. 17 Nov., 1967 [17 Nov., 1966], No. 52388/67. Heading H1D. In a cathode-ray tube having an apertured metallic member such as the shadow-mask in a colour tube, the metallic member contains an occluded gas such as hydrogen or nitrogen which is continually released in operation of the tube under electron bombardment to maintain a partial pressure, e.g. 10 -8 torr, of the gas not more than one magnitude below the total pressure, e.g. 10 -7 torr. This is in order to maintain optimum electron emission and to improve tube life. The gas may be introduced from an external source before sealing of the tube or released from e.g. zirconium or titanium hydride contained within a ring structure also containing getter material, e.g. BaA1. The hydrogen is released first so that subsequent evaporation of the getter at a higher temperature secures a more uniform deposition of the getter on the metallic member and on adjacent parts of the envelope wall. Argon is usually present contributing to the total gas pressure.
TL;DR: The Klopfer ionization gauge as mentioned in this paper was designed to operate either as a total or partial pressure instrument and has a low x-ray limit, low electron current, and a sensitivity for nitrogen of 25 ǫTorr−1.
Abstract: Partly because of a supposed simplicity, omegatrons have been used frequently in applications requiring a light-weight or low-volume mass spectrometer. The present gauge was suggested by the Klopfer ionization gauge, which is similar to an omegatron in its electrode arrangement. The design, construction, and operation of an omegatron is reported here which was designed for operation either as a total or partial pressure instrument. It has a low x-ray limit, low electron current, and a sensitivity for nitrogen of 25 Torr−1. As a total pressure gauge, the ionizing electrons have a more nearly constant energy than other gauges, making it in effect a crude ionization cross-section measuring device. Internal shielding of the ion collector and choice of operating parameters to avoid important spurious effects are considered. The performance is compared to other gauges in argon and nitrogen.
TL;DR: In this paper, a single-pulse shock tube was used for thermolysis of dilute mixtures of 1,1-C2H2F2 in argon at 1290-1480K, 440kN m −2 total pressure, and reaction times of ca. 1 ms.
Abstract: Thermolysis of dilute mixtures of 1,1-C2H2F2 in argon in a single-pulse shock tube at 1290–1480K, 440kN m–2 total pressure, and reaction times of ca. 1 ms yields monofluoroacetylene with an activation energy of ca. 335 kJ mol–1.
TL;DR: In this article, the mean flow of an incompressible fluid in a straight suction duct with porous walls is considered and relations between the inflow and the pressure difference required to produce it are established on the basis of an elementary momentum analysis.
Abstract: The mean flow of an incompressible fluid in a straight suction duct with porous walls is considered and relations between the inflow and the pressure difference required to produce it are established on the basis of an elementary momentum analysis. It is assumed that bom the velocity and the pressure across planes normal to the direction of the mean flow inside the duct are distributed uniformly everywhere and that the effect of obstructions, which do not alter significantly the area of the duct cross section at any position, can be described in terms of losses of total pressure which are proportional to the square of the local speed within the duct. A variety of cases is discussed and it is shown that calculation of the internal pressure is straightforward and in agreement with experiment, at least for the case of a pipe having uniform porosity.
TL;DR: In this paper, the authors ask themselves the following questions: Do we really understand what is meant by 10 5 torr, and is this figure really necessary for an appreciation of the results of the experiment?
Patent•
03 Jun 1970
TL;DR: In this article, the authors present a system for testing and calibrating air data instruments, such as altimeters and air speed indicators, using a transducer-carrier worm wheel.
Abstract: 1,193,841. Testing air pressure gauges. TEXAS INSTRUMENTS Inc. July 10, 1967 [July 15, 1966], No.31585/67. Heading G1L. In apparatus for testing and calibrating air data instruments, such as altimeters, the interior of a Bourdon tube 10a of a unit B is highly evacuated and then plugged 27 and starting from a "null" position of a transducer 12a knob 48, Fig. 2, will be turned to rotate a transducer-carrier worm wheel 15 by the angular degree as indicated on the counter 47 previously calculated as corresponding to absolute atmospheric pressure existing at a predetermined altitude, and with an arm 55 of a meter switch on a servo-contact 56 light reflected from a mirror 30a will fall unevenly on photo-cells within and beyond (51, 52) the transducer 12a and cause a current to pass through a line 50, which current, amplified, will pass through a servocontrol switch contact 39 to a motor 35 to actuate a regulator valve of a regulator 14a to allow gas to pass to a pump 18 from a space in a capsule 9a about the Bourdon tube 10a to cause the capsule 9a pressure to be maintained and the mirror 30a to be rotated to its null position and then disconnect current flow through the line 50. Thus the pressure standard will be maintained constant by the regulator and supplied to the altimeter to be calibrated. The polarity of the currents supplied will be such to operate the motor 35 in the correct direction to connect either a pressure source 19 to the vacuum pump or the vacuum pump 18 to the interior of the capsule 9a. To provide a test standard pressure for an air speed indicator at a particular altitude the interior of a capsule 9 is charged at the absolute pressure existing at the altitude and a transducercarrier worm wheel associated with the capsule 9, is rotated, to the calculated angular degree which would result when the Bourdon tube 10 is subjected to the total or pivot tube pressure at a predetermined test air speed at that altitude. For this purpose, the absolute atmospheric pressure at the altitude being considered, as generated by unit B, is transmitted by branch line 26 to a fitting 5. Then servoamplifier 13 and regulator 14, including parts 55, 58, 40, 35 and 34, Fig. 2, will be operated to automatically direct fluid-pressure from source 19 or vacuum from pump 18 into the interior of Bourdon tube 10 to rotate the mirror 30 to the "null" position with respect to optical transducer 12. The resultant standard test pressure will be held by the regulator mechanism and a pressure supplied through piping 24 will be the total pressure of the air speed to which the meter is being calibrated, while the absolute atmospheric pressure will be transmitted to line 23 to its proper fitting. As before incremental air speeds will be checked to fully calibrate the air speed unit. Other absolute and differential pressure instruments may be calibrated by the apparatus, including mach meters and pressure ratio transducers. The instrument may also be utilized for measuring unknown perameters to simulate an accurately calibrated instrument such as altimeters or air speed meters.
01 Jan 1970
TL;DR: In this paper, the coefficient of lateral pressure referred to the normal axes, Px is the total pressure on the side wall, s is the surface area of the compact in plan, b and h are, respectively, the compact width and height, and Pm is the :mean compaction pressure over the compact height, determined with the formula:
Abstract: ,,~ = bhpm �9 0 ) Here v x is the coefficient of lateral pressure referred to the normal axes, Px is the total pressure on the side wall, s is the surface area of the compact in plan, b and h are, respectively, the compact width and height, and Pm is the :mean compaction pressure over the compact height, determined with the formula:
Journal Article•
TL;DR: In this article, the rotational lines of the N2 molecule in the radiation of a glow discharge in the pure gas, at pressure 0.1-5 torr or with argon, at a total pressure of 2 torr, at current of 40 mA.
Abstract: The intensity distribution was measured for the rotational lines of the N2 molecule in the radiation of a glow discharge in the pure gas, at pressure 0.1–5 torr, or with argon, at a total pressure of 2 torr, at a current of 40 mA. The distribution found lags behind a Boltzmann distribution in the 0–3 band (corresponding to the C3π-B3π transition; the second positive system) over the pressure range 0.1–2 torr and in the 1–4 band (the C3π-B3π transition; second positive system) at a pressure of 0.1 torr. In the N2 + Ar mixture there is selective amplification of the J=25, 26 rotational lines.