Showing papers on "Total pressure published in 1982"

Transient characteristics of a centrifugal pump during stopping period

Abstract: A theoretical and experimental study has been made on the transient characteristics of a centrifugal pump during its rapid acceleration from standstill to final speed Instantaneous rotatinal speed, flow-rate, and total pressure rise are measured for various start-up schemes Theoretical calculations for the prediction of transient characteristics are developed and compared with the corresponding experimental results As the results of this study, it becomes clear that the impulsive pressure and the lag in circulation formation around impeller vanes play predominant roles for the difference between dynamic and quasi-steady characteristics of turbopump during its starting period

Steady Expiratory Flow-Pressure Relationship in a Model of the Human Bronchial Tree

Abstract: Static pressure differences across a human bronchial tree model were obtained for steady expiratory flows of several gases producing Reynolds numbers (Re1) in the bronchus carrying the entire flow (first bronchus) between 150 and 50,000. The model was constructed from an air-dried lung and was complete to bronchi about 2 mm in diameter. Dimensionless static pressure plotted against Re1 consolidated the data on a single curve, phenomenologically described by an equation of the form: delta Ps/delta Pd1 = A + B Re1 where delta P d1 is a pressure drop for Poiseuille flow, Velocity profile measurements at two sites along the first bronchus for laminar and turbulent flows indicate a dependence on the latter and distance from the first junction. Loss in total pressure was computed and may result from both frictional dissipation and changes in momentum flux associated with development of velocity profiles near the junctions. An average loss in total pressure within a single bronchus was calculated after making several simplifying assumptions, and this result may be useful in modeling both the resistance of the entire bronchial tree and the more complex phenomenon of maximal expiratory flow.

Total pressure probe

Abstract: Total Pressure Probe Abstract A pressure probe 26 for sensing total pressure in a duct 16, 22 bounding a flow path 12 for a working medium fluid is disclosed. The probe has an alignment portion 32, a sensor portion 34 spaced from the align-ment portion leaving a plenum 36 therebetween and passageways 41 for ducting the flow away from the plenum. In one particular embodiment a transition passageway 54 extends between the plenum and the passageway 41. The alignment portion has a first passageway 42 directed towards a second passageway 40 in the sensor portion. The sensor portion has a wall 38 disposed about the second passageway 40. A method is disclosed for sensing total pressure which includes the steps of: diverting a portion of the flow from the working medium flow path to the pres-sure probe; converting the total pressure of the diverted flow to a static pressure and to a velocity pressure wherein the velocity pressure results from flow along streamlines parallel to the first pas-sageway; impacting substantially all of the diverted portion of the flow against the sensor portion in the wall region bounding the plenum; and, sensing the static pressure of the flow in the wall region of the plenum to sense total pressure; and ducting all of the diverted flow away from the plenum.

Non-dispersive optical determination of gas concentration

Abstract: Apparatus (FIG. 1) for non-dispersive optical determination of the concentration of an identifiable gas, such as a hydrocarbon, in a mixture such as atmospheric air comprises a sample chamber 13 to contain a sample of the mixture, a source 21 of IR radiation at a wavelength absorbed by the gas beamed through the sample chamber to a detector 22 and transducer means to change the gas pressure within the chamber to determine the change in radiation intensity detected at different pressures. One wall of the sample chamber is formed by a flexible diaphragm 25 driven by a voice-coil type transducer 26 whereby the pressure is switched repetitively between the values above and below atmospheric. Atmospheric gas is admitted to the chamber by a porous plug 24 which restricts flow to a low level permitting a pressure change in the chamber. Absorption by the gas relates the intensity of source radiation I S and measured radiation I M by I M oc I S ·e - α o.sup.·g·p·x where x is the radiation path length through the sample, α o is a constant, p the total pressure of the gas mixture and g the concentration of the hydrocarbon gas. By measuring intensity at different pressure involving a change Δp and a fractional change in intensity of measured radiation ΔI/I, the gas concentration g is determined by applying the relationship:- g=-ΔI/(I·Δp·α o ·x).

Morphological fluctuation and electrical properties of sputtered hydrogenated silicon

Abstract: Electrical properties and x‐ray small angle scattering have been measured on rf‐sputtered Si:H alloys deposited at various hydrogen partial pressures of argon and hydrogen mixture gas with a constant total pressure. When the hydrogen partial pressure exceeds 40%, microcrystalline zone of about 200 A in diameter is formed and photoexcited carriers show nondispersive transport, instead of dispersive transport which is typical of rf‐sputtered a‐Si:H.

Method of measuring an air to fuel ratio

Abstract: A method is disclosed for measuring the air to fuel ratio of an air/fuel mixture being supplied to a combustion process. This method has the following steps. An oxygen sensor station is established at which the sensor senses the difference in oxygen partial pressure from a first reference side thereof to a second oxygen measurement side thereof. The oxygen sensor is maintained at a predetermined temperature and at a pressure below atmospheric pressure. The oxygen sensor is calibrated so that the measurement thereby of an EMF between the first reference side thereof and the second oxygen measurement side thereof is indicative of the oxygen partial pressure in a gas stream passing by the oxygen measurement side thereof. A sample gas stream is drawn into the pressure across the second oxygen measurement side of the oxygen sensor. This pressure is one which allows samples to be drawn at a constant flow rate independent of that pressure. A fixed amount of oxygen is added to the sample gas stream. The oxygen in the sample gas stream is reacted with oxidizable species contained in the sample gas stream prior to passing the sample gas stream across the second oxygen measurement side of the oxygen sensor. The pressure of the gas sample is measured. The air to fuel ratio of the air/fuel mixture is determined from the measured EMF of the oxygen sensor, the total pressure of the sample gas stream and the known oxygen addition rate. Suitable oxygen sensors may be formed zirconia or titania.

Theory and calibration of non-nulling seven-hole cone probes for use in complex flow measurement

Abstract: A seven-hole conical pressure probe capable of measuring flow conditions at angles up to 75 deg relative to its axis is described. The theoretical rationale of the seven-hole probe is developed and the calibration procedure outlined. Three-variable third order polynomials are used to represent local values of total pressure, static pressure, Mach number and relative flow angles. These flow conditions can be determined explicitly from measured probe pressures. Flow angles may be determined within 2.5 deg and Mach number within 0.05 with 95% certainty. The probe was calibrated in subsonic compressible and incompressible flows. Results of a calibration of four seven-hole probes are presented.

Effect of steady-state pressure distortion on inlet flow to a high-bypass-ratio turbofan engine

Abstract: The effects of circumferential inlet temperature distortion on the flow characteristics between a distortion generator and a high bypass ratio turbofan engine and through its compression system were evaluated to support the effort to generate analytical models The flow characteristics are defined by the inlet duct, the flow angles, and the total temperature, total pressure, and static pressure profiles in the inlet duct and through the fan and compressor The effects of Reynolds number, rotor speed, and distortion extent are also considered

Total pressure dependence of doping element incorporation during the chemical vapour deposition of epitaxial silicon

Abstract: Starting from the literature on doping element incorporation at atmospheric and lower pressures the partial pressure of the dopants available within the deposition system is selected as a uniform basis of reference for the total pressure dependence of the doping element incorporation. It is shown that also at reduced pressures the incorporation equilibria of phosphor and arsenic, the author previously derived from the temperature dependence of the doping element incorporation may be used.

Unsteady Three-Dimensional Turbine Aerodynamics

Abstract: High response aerodynamic measurements were made in a large scale, axial, flow turbine model to study the unsteadiness and three dimensionality of the flow. High response velocity vector and total pressure data were acquired. A comparison was made of the results of phase lock, averaging both raw and reduced data (voltages and velocities). The velocity vector measurements showed that there were strong radial flows present as well as significant periodic changes in the flow field due to relative rotor and vane positions. Random, periodic, and total unsteadiness levels were computed from the instantaneous and phase lock averaged velocity data. Time averaged data were compared with an inviscid two-dimensional calculation. A comparison was also made of time averaged total pressure measurements obtained from high response and low response (steady-state) probes.Copyright © 1982 by ASME

Experimental Pressure Profiles Along the Vapor Channel of a Flat-Plate Heat Pipe

Abstract: An experimental flat-plate heat pipe with an adiabatic top plate has been constructed to study the vapor flow. The heat pipe is operated around 15°C with water as the working fluid. Longitudinal pressure profiles in the rectangular vapor channel have been measured for values of the radial Reynolds number Rer of 3.7, 5.7 and 6.6. The profiles agree well with those predicted with a simple Poiseuille flow approximation model that is based on the assumption of parabolic velocity profiles for the vapor flow. Still better agreement is found with the results obtained by the computer program TEACH that predicts for the complete heat pipe a 10% larger total pressure drop than does the simple model for Rer = 5. For Rer >5 pressure buildup in the condensation zone is found as predicted.

Ethylene monitoring by differential absorption with a CO 2 waveguide laser

Abstract: In this paper we report on a differential absorption technique using a CO2 waveguide laser The method is based on the measurement of the differential absorption between two different frequencies of the same selected CO2 laser line The sensitivity of the technique depends strongly on the total pressure and has been estimated to be about a few tens of ppb or better over a 1 km path length in C2H4 diluted with air to a total pressure of a few tens of torrs Its relative simplicity and high sensitivity at low total pressure enable this technique to be applied to gas detection either at high altitude or to local monitoring of a low pressure sample

Kinetics of the Reaction NH2 + 1,3‐Butadiene

Abstract: The gas-phase reaction of free NH2 radicals with 1,3-butadiene has been investigated in an isothermal discharge-flow system under pseudo-first-order conditions. NH2 was produced in the fast reaction to fluorine atoms with ammonia and its concentration was monitored by laser-induced fluorescence. For the room temperature measurements at 2 mbar a rate coefficient of 6.7 · 109 cm3 mol−1 s−1 was derived. Temperature and pressure conditions were varied in the range of 230–360 K, and 2–10 mbar, respectively. The temperature dependence can be described in the Arrhenius expression k(T) = 3.8 · 1011 exp(-1140 K/T) cm3 mol−1 s−1. An effect of the total pressure on the rate constant was not observed.

Rheological interpretation of pressure anomalies of aqueous dilute polymer solutions (ADPS) in orifice flow

Abstract: The response of a considerable number of solutions of several polymers (PEO, HPAM, PAM) with concentrations of less than 100 ppm in orifice flow has been investigated. It is shown that the excess pressure (difference between the ADPS and the solvent total pressure drop) behaves linearly as a function of a superficial strain rate (ratio between a velocity and a length scale). In rheological terms this behaviour is interpreted as the result of a constant elongational viscosity whose values are two to three orders of magnitude larger than the shear viscosity. A formal approach to this phenomenological interpretation is suggested.

Total and static pressure measurements of the male lower urinary tract

Abstract: Simultaneous total and static urethral pressure measurements were attempted in 22 male subjects who could void around a 10-French bilumen urethral catheter. The catheter had an end-hole at its tip and a side-hole approximately 1 cm away from the end hole (short catheter-tip segment). Thus, during a single voiding attempt, simultaneous total and static urethral pressures at two different urethral sites (1 cm distance) could be recorded. In addition, suprapubic vesical pressure monitoring was done in all these subjects. The studies also included a comparison of these recordings with those obtained with a 10-French catheter that had its side-hole placed 10 cm away from the tip (long catheter-tip segment). The studies indicated that (1) the total pressure at a particular region of the urethra was usually higher than its static pressure; (2) the pressure sensing catheters produced “plugging effect” of the narrow segments of the outlet; and (3) the static pressure configurations that were obtained with a catheter having a long catheter-tip segment were markedly different from those obtained through a catheter that had a short catheter-tip segment. This presentation also includes observations on static pressure measurements obtained from a crude mechanical model that simulated the geometry of the urinary bladder and its outlet. True lateral pressures of the flowing fluid were obtained via cannulae inserted perpendicularly into the stream, through the wall of the outlet (extraluminal route). A comparison was attempted between the static pressure measurements obtained through the extraluminal route with those obtained through the catheters (10–14 French) that were directly inserted into the lumen of the outlet along its axis (intraluminal route). The studies indicated identical static pressures at the narrowest site (16–18 French) of the outlet recorded through both routes.

Testing method for semiconductor device

Abstract: PURPOSE:To estimate mechanical strength to humidity in a semiconductor device, by estimating the influence of stress generated when a liquid entering a package evaporates. CONSTITUTION:A semiconductor device to be tested whose electric characterisitcs are measured previously is held in a high-temperature, high-humidity atmosphere of 85 deg.C and 85% for 24hr to make water permeate the semiconductor device. The device is put in a 100 deg.C high-temperature chamber within two hours after it is taken out of the said atmosphere, and retained in it for 24hr to vapor the water permeating the devce. As a result of a rest by the said method, when the semiconductor device is, for example, of a can-sealed type, the total pressure of the saturated vapor pressure and internal pressure generates stress strain in the semiconductor device and the influence of the stress upon a semiconductor die, a wire bonding part, a package, etc., is estimated by electric characteristics and internal observation.

Pressure-dependent electron attachment rates in perfluoroalkanes and perfluoropropylene (1-c3f6) and their effect on the breakdown strength of these gases

Abstract: The pressure dependence of the attachment rate constant of several perfluoroalkane dielectrics has been studied in buffer gases of N/sub 2/ and Ar up to a total pressure of 2.4 MPa. It has been observed that the higher order perfluoroalkanes (n-C/sub N/F/sub 2N+2/; 3 less than or equal to N less than or equal to 6) exhibit a marked dependence of their attachment rate constant on the total gas pressure, particularly in the pressure range from 53 kPa to approx. 700 kPa in N/sub 2/ over a mean energy range of from thermal energy to approx. = 1 eV, and in Ar over the energy range from approx. = 0.3 eV to approx. = 4.5 eV. A considerably larger total pressure dependence has been observed for 1-C/sub 3/F/sub 6/ in N/sub 2/ and Ar, which does not saturate, even at the highest buffer gas pressures (3.2 MPa). A partial pressure dependence of the attachment rate on 1-C/sub 3/F/sub 6/ has also been observed in these mixtures, which may saturate above approx. 15 kPa, indicating that the attachment process involves the interaction of two or more 1-C/sub 3/F/sub 6/ molecules. Breakdown measurements have been performed in 1-C/sub 3/F/sub 6/ using uniformmore » field electrodes and in mixtures of 1-C/sub 3/F/sub 6//N/sub 2/ and 1-C/sub 3/F/sub 6//SF/sub 6/ using point-plane electrodes. These measurements have been performed over the total pressure range 25 to 600 kPa. The dc breakdown strength of 1-C/sub 3/F/sub 6/ is dependent on the total gas pressure after allowing for the effect of compressibility of the gas. Our attachment and breakdown measurements for these gases and gas mixtures are reported and discussed.« less

Process for hydrocracking a hydrocarbonaceous feed with hydrogen recovery and recycle

Abstract: Efficient utilization of hydrogen in a hydrocracking system is obtained by recovering in a first gas-liquid separation zone (20) hydrogen by gas-liquid separation of hydrocrackate (14) at a pressure of at least about 75 percent of the pressure in the hydrocracking zone (10), and recovering in a second gas-liquid separation zone (26) hydrogen from the separatea liquid phase (24) from the first gas-liquid separation zone (20), said second gas-liquid separation zone (26) being at a pressure less than 75 percent of the pressure in the first gas-liquid separation zone (20) and at conditions sufficient to provide a separated vapor phase (30) containing at least about 50 volume percent of hydrogen and having a hydrogen partial pressure of at least about 20 atmospheres. At least a portion of the separated vapor phase (30) from the second gas-liquid separation zone (26) is contacted with the feed side of a polymeric membrane, in a permeator (34) exhibiting a high selectivity to the permeation of hydrogen as compared to the permeation of methane. The opposite side, i.e., permeate side, of the membrane is maintained at a pressure sufficiently below the pressure on the feed side of the membrane such that the ratio of the total pressure on the feed side to total pressure on the feed side to total pressure on the permeate side of the membrane is at least about 3:1 to permeate hydrogen to the permeate side of the membrane and provide a hydrogen permeate (38) having a concentration of hydrogen greater than the concentration of hydrogen in the separated vapor phase (30) contacting the membrane. At least a portion of the hydrogen permeate (38) is recycled to the hydrocracking zone (10). Thus, the second gas-liquid separation zone (26) co-acts with the polymeric membrane separation to provide a highly useable, recovered hydrogen stream in the hydrocracking system.

Écoulement dans une turbine Kaplan : comparaison entre calcul théorique, mesures de vitesse et observations de cavitation

Abstract: Experimental and theoretical results of the flow field analysis in a medium specific speed Kaplan turbine model are presented. The five analysed operating points which have been obtained with the two runner blade openings of maximum efficiency and maximum prototype power are shown in figure 1. The experimental analysis consists of velocity and total pressure measurements by means of bidirectional probes in three sections upstream and one downstream of the runner (Fig. 2), and of observations and photos of the cavitated zones on the blade surfaces and in the blade channels for different values of the σu cavitation coefficient. The quasi-threedimensional analysis of the flow field included between the guide vane inlet and section 4 has been carried out utilizing for the meridional calculation a computer program based on the method of fixed projection lines [3] and for the blade-to-blade calculation a program based on the method of integral equations [4]. The results of the meridional calculation have been compared with the experirnental results of the four measuring sections for the five operating points. As an example, the comparison relevant to point D is reported in figure 3. In the upstream stations, for all operating points, the velocity percentile differences do not reach 10 % and the differences of the β angle are not larger than 60 near the hub and 20 at the tip. In the downstream station the maximum difference of the β angles is less than 2. At point D blade-to-blade calculations have been performed assigning both the theoretical and experimental upstream velocity distributions in order to evidence the effects of the errors of the upstream velocity on the blade pressure distribution (Fig. 4). The downstream tangential absolute velocity (Fig. 5) and total pressure distributions (Fig. 6) indicate that a regular distribution of work extraction along the blade height has been obtained with a downstream tangential velocity distribution which is favourable from the point of view of the outlet kinetic energy losses and of the losses in the draft tube. The computed distribution of the Cp coefficient drawn on the front view of the blade for all the operating points (Fig. 7 to 11), allows to visualize irnmediately the theoretical cavitation zone for each value of σu, In fact, the static pressure coefficient Cp has been defined in such a way (see the definition in the text) that Cp is equal to - σu when the local static pressure reaches the vapour pressure. An exact prediction of the extension of the cavitating regions cannot be obtained because the method does not take into account the effect of the vapour bubbles on the pressure distribution, but a general nearly good agreement of the calculations with the cavitation configurations has been found. Two different types of leading edge cavitation have been observed : a burst type near the hub, characterized by a very strong pressure gradient (Fig. 12, fc = 0.15), and a fixed type connected with a weaker pressure gradient at the tip (Fig. 12, fc = 0.85).

Manufacture of thin silicon carbide film

Abstract: PURPOSE:To form a thin SiC film of high hardness at a relatively low temp. by keeping the partial pressure of each reactive gas at a specified low value in the manufacture of a thin SiC film by a plasma CVD method. CONSTITUTION:A reactor 1 in which a substrate 3 is mounted on a holder 2 is well evacuated with an exhaust system 4, and the substrate 3 is heated to about 300- 400 deg.C with a heating source 5. Ar is introduced into the reactor 1 from a gas feeder 6, and plasma is generated with a plasma generating equipment composed of a high frequency power source 7, a matching box 9 and electrodes 9 to clean the surface of the substrate 3. A gaseous mixture of silane, mehtane and Ar is then introduced into the reactor 1 after regulating the total pressure of the partial pressure of gaseous silane and that of gaseous methane to 1.3-15pa, and plasma is generated at about 130-260pa vacuum degree and about 100W high frequency power to deposit SiC on the surface of the substrate 3.