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Journal articles on the topic 'Low pressure part'

Author: Grafiati

Published: 4 June 2021

Last updated: 3 February 2022

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1

Brear, Michael J., Howard P. Hodson, and Neil W. Harvey. "Pressure Surface Separations in Low-Pressure Turbines—Part 1: Midspan Behavior." Journal of Turbomachinery 124, no. 3 (July 1, 2002): 393–401. http://dx.doi.org/10.1115/1.1450764.

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This paper describes an investigation into the behavior of the pressure surface separation at midspan in a linear cascade. It is found that the pressure surface separation can be a significant contributor to the profile loss of a thin, solid, low-pressure turbine blade that is typical of current engine designs. Numerical predictions are first used to study the inviscid behavior of the blade. These show a strong incidence dependence around the leading edge of the profile. Experiments then show clearly that all characteristics of the pressure surface separation are controlled primarily by the incidence. It is also shown that the effects of wake passing, freestream turbulence and Reynolds number are of secondary importance. A simple two-part model of the pressure surface flow is then proposed. This model suggests that the pressure surface separation is highly dissipative through the action of its strong turbulent shear. As the incidence is reduced, the increasing blockage of the pressure surface separation then raises the velocity in the separated shear layer to levels at which the separation can create significant loss.

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2

Straka, František, Pavel Pánek, and Pavel Albl. "Plastic Behavior of Steam Turbine Low Pressure Part." Applied Mechanics and Materials 827 (February 2016): 197–200. http://dx.doi.org/10.4028/www.scientific.net/amm.827.197.

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Low-pressure steam turbine parts are generally exposed to lowest steam parameters only and it could seem that they should not be susceptible to permanent deformation. However, this assumption is incorrect and permanent changes in geometry become visible in low-pressure turbine casings when they are disassembled after the first time in operation. The driving mechanism of the plastic deformation of the low-pressure casings is mainly the non-uniform temperature field. This paper deals with results obtained from a numerical FEM simulation of a steam turbine low pressure part, which includes elastic-plastic behavior of the material, and results measured under the real conditions.

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3

Purushothaman, B. K., and J. S. Wainright. "Analysis of pressure variations in a low-pressure nickel–hydrogen battery: Part 1." Journal of Power Sources 206 (May 2012): 429–35. http://dx.doi.org/10.1016/j.jpowsour.2012.01.150.

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4

Brear, Michael J., Howard P. Hodson, Paloma Gonzalez, and Neil W. Harvey. "Pressure Surface Separations in Low-Pressure Turbines—Part 2: Interactions With the Secondary Flow." Journal of Turbomachinery 124, no. 3 (July 1, 2002): 402–9. http://dx.doi.org/10.1115/1.1450765.

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This paper describes a study of the interaction between the pressure surface separation and the secondary flow on low-pressure turbine blades. It is found that this interaction can significantly affect the strength of the secondary flow and the loss that it creates. Experimental and numerical techniques are used to study the secondary flow in a family of four low-pressure turbine blades in linear cascade. These blades are typical of current designs, share the same suction surface and pitch, but have differing pressure surfaces. A mechanism for the interaction between the pressure surface separation and the secondary flow is proposed and is used to explain the variations in the secondary flows of the four blades. This mechanism is based on simple dynamical secondary flow concepts and is similar to the aft-loading argument commonly used in modern turbine design.

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5

Bredmose, H., G. N. Bullock, and A. J. Hogg. "Violent breaking wave impacts. Part 3. Effects of scale and aeration." Journal of Fluid Mechanics 765 (January 16, 2015): 82–113. http://dx.doi.org/10.1017/jfm.2014.692.

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AbstractThe effects of scale and aeration on violent breaking wave impacts with trapped and entrained air are investigated both analytically and numerically. By dimensional analysis we show that the impact pressures for Froude scaled conditions prior to the impact depend on the scale and aeration level. The Bagnold–Mitsuyasu scaling law for the compression of an air pocket by a piston of incompressible water is rederived and generalised to 3D air pockets of arbitrary shape. Numerical results for wall pressure, force and impulse are then presented for a flip-through impact, a low-aeration impact and a high-aeration impact, for nine scales and five levels of initial aeration. Two of these impact types trap a pocket of air at the wall. Among the findings of the paper is that for fixed initial aeration, impact pressures from the flip-through impact broadly follow Froude scaling. This is also the case for the two impact types with trapped air pockets for impact pressures below 318 kPa, while impact pressures above this value broadly follow the Bagnold–Mitsuyasu scaling law with full-scale pressures greater than those predicted by the Froude law. For all impact types, the effect of aeration is found to reduce the maximum impact pressure, maximum force and impulse. Good agreement with the asymptotic model of Peregrine & Thais (J. Fluid Mech., vol. 325, 1996, pp. 377–397) is found for the flip-through impact pressure and a fair agreement is found for the low- and high-aeration impacts. Based on the numerical results, a modified scaling curve that combines Froude scaling and the Bagnold–Mitsuyasu law is suggested. The practical implications of the findings are discussed and attention is drawn to the limitations of physical model tests.

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6

Harman, C. M., and S. Loesch. "Energy Storage Using Low-Pressure Feedwater." Journal of Engineering for Gas Turbines and Power 107, no. 3 (July 1, 1985): 569–73. http://dx.doi.org/10.1115/1.3239774.

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A method for increasing the peak output of steam power plants through use of a low-pressure feedwater storage system is presented. The generalized availability analysis involves only the low-pressure turbine, low-pressure feedwater heaters, and the storage system. With daily cycling and storage charging at near base load conditions, the turnaround efficiency of the energy storage system was found to approach 100 percent. Storage system turnaround efficiency is decreased when the energy is stored during plant part-load operation.

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7

KAWASAKI, Hiroshi, Tadashi KATO, Soichiro IMADA, Hideaki MIWA, and Tadashi YAMADA. "Low Pressure Koch Reaction by Cu(CO)n+-H2SO4-H3PO4-H2O Catalyst(Part 1). Low Pressure Koch Reaction of Isobutylene Oligomers." Journal of The Japan Petroleum Institute 37, no. 3 (1994): 255–60. http://dx.doi.org/10.1627/jpi1958.37.255.

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8

O'Connell, Deborah, Timo Gans, Albert Meige, Peter Awakowicz, and Rod W. Boswell. "Plasma Ionization in Low-Pressure Radio-Frequency Discharges. Part I: Optical Measurements." IEEE Transactions on Plasma Science 36, no. 4 (August 2008): 1382–83. http://dx.doi.org/10.1109/tps.2008.927348.

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9

Cooper, E. W., and D. W. Etheridge. "Determining the adventitious leakage of buildings at low pressure. Part 1: uncertainties." Building Services Engineering Research and Technology 28, no. 1 (February 2007): 71–80. http://dx.doi.org/10.1177/0143624406072330.

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10

Chang, C. H., and E. Pfender. "Nonequilibrium modeling of low-pressure argon plasma jets; Part I: Laminar flow." Plasma Chemistry and Plasma Processing 10, no. 3 (September 1990): 473–91. http://dx.doi.org/10.1007/bf01447204.

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11

Chang, C. H., and E. Pfender. "Nonequilibrium modeling of low-pressure argon plasma jets; Part II: Turbulent flow." Plasma Chemistry and Plasma Processing 10, no. 3 (September 1990): 493–500. http://dx.doi.org/10.1007/bf01447205.

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12

Lurie, Fedor. "Low Interface Pressure Provides Major Part of Hemodynamic Response to Compression Therapy." European Journal of Vascular and Endovascular Surgery 57, no. 5 (May 2019): 708. http://dx.doi.org/10.1016/j.ejvs.2019.01.020.

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13

Szpica, Dariusz, and Michał Kusznier. "Modelling of the Low-Pressure Gas Injector Operation." Acta Mechanica et Automatica 14, no. 1 (March 1, 2020): 29–35. http://dx.doi.org/10.2478/ama-2020-0005.

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AbstractIn recent years, there has been a growing interest in alternative sources of power supply for internal combustion engines. Liquefied petroleum gas injection systems are among the most popular. It becomes necessary to know mathematical descriptions of the operation of individual components. The article presents a mathematical model that describes the operation of the low-pressure gas injector. Valtek plunger injector was chosen as the test object. The mathematical description includes three parts, i.e. electric, mechanical and pneumatic. The electrical part describes the generation of electromagnetic force by a circuit with a coil, in the mechanical equilibrium equation of forces acting on the plunger, and in the pneumatic part the air pressure on the plunger. The calculations were performed in the Matlab/Simulink environment, creating current waveforms, acting forces and plunger displacement. Correctness of mathematical description and determined in the course of opening and closing time calculations were related to the values declared by the manufacturer, showing differences below 3%. The presented mathematical model can be modified for other injector design solutions.

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14

Schoof, Christian, Ian J. Hewitt, and Mauro A. Werder. "Flotation and free surface flow in a model for subglacial drainage. Part 1. Distributed drainage." Journal of Fluid Mechanics 702 (May 23, 2012): 126–56. http://dx.doi.org/10.1017/jfm.2012.165.

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AbstractWe present a continuum model for melt water drainage through a spatially distributed system of connected subglacial cavities, and consider in this context the complications introduced when effective pressure or water pressure drops to zero. Instead of unphysically allowing water pressure to become negative, we model the formation of a partially vapour- or air-filled space between ice and bed. Likewise, instead of allowing sustained negative effective pressures, we allow ice to separate from the bed at zero effective pressure. The resulting model is a free boundary problem in which an elliptic obstacle problem determines hydraulic potential, and therefore also determines regions of zero effective pressure and zero water pressure. This is coupled with a transport problem for stored water, and the coupled system bears some similarities with Hele-Shaw and squeeze-film models. We present a numerical method for computing time-dependent solutions, and find close agreement with semi-analytical travelling wave and steady-state solutions. As may be expected, we find that ice–bed separation is favoured by high fluxes and low ice surface slopes and low bed slopes, while partially filled cavities are favoured by low fluxes and high slopes. At the boundaries of regions with zero water or effective pressure, discontinuities in water level are frequently present, either in the form of propagating shocks or as stationary hydraulic jumps accompanied by discontinuities in potential gradient.

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15

Krzyżanowski, J. "On efficiency measurements for large steam turbine low-pressure stages." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 211, no. 4 (June 1, 1997): 347–55. http://dx.doi.org/10.1243/0957650971537259.

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Current trends in the development of power engineering are turning attention towards modernization of the machinery and equipment. Modernization of the LP (low-pressure) part of a turbine is one of the most promising solutions. A natural question which arises concerns the effectiveness of such modernization, i.e. a comparison of the characteristics (efficiency) of this turbine part before and after modernization. Such a comparison may be based on measurements of the efficiency of the LP part and the last stage before and after the modernization, provided that the efficiency gain achieved exceeds the measuring error. This paper deals with the estimation of the accuracy of such a measurement, the principle and methodology of which have been developed at the Institute of Fluid-Flow Machinery (IFFM) for a real turbine.

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16

Verweij, J. M., H. J. Simmelink, J. Underschultz, and N. Witmans. "Pressure and fluid dynamic characterisation of the Dutch subsurface." Netherlands Journal of Geosciences - Geologie en Mijnbouw 91, no. 4 (December 2012): 465–90. http://dx.doi.org/10.1017/s0016774600000342.

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AbstractThis paper presents and discusses the distribution of fluid and leak-off pressure data from the subsurface of onshore and offshore Netherlands in relation to causes of formation fluid overpressure and the permeability framework. The observed fluid pressure conditions demonstrate a clear regional difference between the southern and the north and north-eastern part of the study area. In the southern area, formation fluid pressures are close to normal and well below measured leak-off pressures. In the north, formation fluids are overpressured and may locally even approach the measured leak-off pressures. The regional differences in fluid overpressure can, in large part, be explained by differences in geologic framework and burial history. In the south, relatively low rates of sedimentary loading and the presence of relatively permeable sedimentary units have led to the currently observed normally pressured conditions. In the northern area, relatively rapid Neogene sediment loading plays an important role in explaining the observed overpressure distributions in Cenozoic mudstones, Cretaceous Chalk and Rijnland groups, and probably also in Jurassic units. The permeability framework of the northern and north-eastern area is significantly affected by Zechstein and Triassic salt deposits and structures. These units are characterised by very low permeability and severely restrict fluid flow and pressure dissipation. This has created hydraulically restricted compartments with high overpressures (for example overpressures exceeding 30 MPa in the Lower Germanic Trias Group in the Terschelling Basin and Dutch Central Graben).

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17

Nowinski, M., and J. Panovsky. "Flutter Mechanisms in Low Pressure Turbine Blades." Journal of Engineering for Gas Turbines and Power 122, no. 1 (October 20, 1999): 82–88. http://dx.doi.org/10.1115/1.483179.

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The work described in this paper is part of a comprehensive research effort aimed at eliminating the occurrence of low pressure turbine blade flutter in aircraft engines. The results of fundamental unsteady aerodynamic experiments conducted in an annular cascade are studied in order to improve the overall understanding of the flutter mechanism and to identify the key flutter parameters. In addition to the standard traveling wave tests, several other unique experiments are described. The influence coefficient technique is experimentally verified for this class of blades. The beneficial stabilizing effect of mistuning is also directly demonstrated. Finally, the key design parameters for flutter in low pressure turbine blades are identified. In addition to the experimental effort, correlating analyses utilizing linearized Euler methods demonstrate that these computational techniques are adequate to predict turbine flutter. [S0742-4795(00)01301-6]

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18

Mailach, Ronald, and Konrad Vogeler. "Rotor-Stator Interactions in a Four-Stage Low-Speed Axial Compressor—Part I: Unsteady Profile Pressures and the Effect of Clocking." Journal of Turbomachinery 126, no. 4 (October 1, 2004): 507–18. http://dx.doi.org/10.1115/1.1791641.

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This two-part paper presents detailed experimental investigations of unsteady aerodynamic blade row interactions in the four-stage Low-Speed Research Compressor of Dresden. In part I of the paper the unsteady profile pressure distributions for the nominal setup of the compressor are discussed. Furthermore, the effect of blade row clocking on the unsteady profile pressures is investigated. Part II deals with the unsteady aerodynamic blade forces, which are calculated from the measured profile pressure distributions. The unsteady pressure distributions were analyzed in the first, a middle and the last compressor stage both on the rotor and stator blades. The measurements were carried out on pressure side and suction side at midspan. Several operating points were investigated. A complex behavior of the unsteady profile pressures can be observed, resulting from the superimposed influences of the wakes and the potential effects of several up- and downstream blade rows of the four-stage compressor. The profile pressure changes nearly simultaneously along the blade chord if a disturbance arrives at the leading edge or the trailing edge of the blade. Thus the unsteady profile pressure distribution is nearly independent of the convective wake propagation within the blade passage. A phase shift of the reaction of the blade to the disturbance on the pressure and suction side is observed. In addition, clocking investigations were carried out to distinguish between the different periodic influences from the surrounding blade rows. For this reason the unsteady profile pressure distribution on rotor 3 was measured, while stators 1–4 were separately traversed stepwise in the circumferential direction. Thus the wake and potential effects of the up- and downstream blade rows on the unsteady profile pressure could clearly be distinguished and quantified.

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19

Shalem, C. K., R. Chechik, A. Breskin, K. Michaeli, and N. Ben-Haim. "Advances in thick GEM-like gaseous electron multipliers Part II: Low-pressure operation." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 558, no. 2 (March 2006): 468–74. http://dx.doi.org/10.1016/j.nima.2005.12.219.

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20

Cooper, E. W., D. W. Etheridge, and S. J. Smith. "Determining the adventitious leakage of buildings at low pressure. Part 2: pulse technique." Building Services Engineering Research and Technology 28, no. 1 (February 2007): 81–96. http://dx.doi.org/10.1177/0143624406072331.

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21

Nikolić, Dragan, Stojan M. Madzunkov, and Murray R. Darrach. "Computer Modeling of an Ion Trap Mass Analyzer, Part I: Low Pressure Regime." Journal of The American Society for Mass Spectrometry 26, no. 12 (August 19, 2015): 2115–24. http://dx.doi.org/10.1007/s13361-015-1236-5.

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22

Guillot, Bertrand, and Nicolas Sator. "A computer simulation study of natural silicate melts. Part I: Low pressure properties." Geochimica et Cosmochimica Acta 71, no. 5 (March 2007): 1249–65. http://dx.doi.org/10.1016/j.gca.2006.11.015.

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23

Calabrese, Edward J., and Robert W. Tuthill. "The Massachusetts Blood Pressure Study, Part 3. Experimental Reduction of Sodium in Drinking Water: Effects On Blood Pressure." Toxicology and Industrial Health 1, no. 1 (January 1985): 19–34. http://dx.doi.org/10.1177/074823378500100103.

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An experimental bottled water study assessed the effect on blood pressure of lowering Na concentration in the water of some of the high sodium community fourth graders. For three months, trios of children matched by sex, school, and baseline BP each used different water for all cooking and drinking purposes, with BP monitored bi-weekly. Pupils were randomly allocated to the three water conditions: (1) high sodium water bottled from their own community distribution system, (2) low sodium water bottled from the distribution system of the comparison community with sodium added to the level of the high sodium community water and (3) low sodium water bottled from the distribution system of the low sodium community but with no sodium added. The results indicate that BP levels among the girls but not boys on the low sodium water exhibited marked decreases in BP over the test period when compared to the other two groups.

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24

Lawless, P. B., and S. Fleeter. "Rotating Stall Acoustic Signature in a Low-Speed Centrifugal Compressor: Part 1—Vaneless Diffuser." Journal of Turbomachinery 117, no. 1 (January 1, 1995): 87–96. http://dx.doi.org/10.1115/1.2835646.

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An experimental study is performed to identify spatially coherent pressure waves, which would serve as precursors to the development of an instability in the Purdue Low-Speed Centrifugal Research Compressor when configured with a vaneless diffuser. To achieve this, sensitive electret microphones were uniformly distributed around the circumference in the inlet and diffuser sections of the compressor. Fourier analysis of simultaneously sampled data from these microphone arrays was employed to identify the development of dominant spatial modes in the pressure field in the compressor. The transition to stall was observed to be a gradual process, with the growth of the pressure waves into those corresponding to a large-scale stall condition occurring over a time span of 26 impeller revolutions. The excitation of the pressure waves, as indicated by spatial Fourier analysis, occurred 14 impeller revolutions before small changes were evident in the microphone signals, and 26 revolutions before the stall condition could be considered fully developed.

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25

TINNEY, C. E., L. S. UKEILEY, and M. N. GLAUSER. "Low-dimensional characteristics of a transonic jet. Part 2. Estimate and far-field prediction." Journal of Fluid Mechanics 615 (November 25, 2008): 53–92. http://dx.doi.org/10.1017/s0022112008003601.

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Complementary low-dimensional techniques are modified to estimate the most energetic turbulent features of a Mach 0.85 axisymmetric jet in the flow's near-field regions via spectral linear stochastic estimation. This model estimate is three-dimensional, comprises all three components of the velocity field and is time resolved. The technique employs the pressure field as the unconditional input, measured within the hydrodynamic periphery of the jet flow where signatures (pressure) are known to comprise a reasonable footprint of the turbulent large-scale structure. Spectral estimation coefficients are derived from the joint second-order statistics between coefficients that are representative of the low-order pressure field (Fourier-azimuthal decomposition) and of the low-order velocity field (proper orthogonal decomposition). A bursting-like event is observed in the low-dimensional estimate and is similar to what was found in the low-speed jet studies of others. A number of low-dimensional estimates are created using different velocity–pressure mode combinations from which predictions of the far-field acoustics are invoked using Lighthill's analogy. The overall sound pressure level (OASPL) directivity is determined from the far-field prediction, which comprises qualitatively similar trends when compared to direct measurements at r/D=75. Retarded time topologies of the predicted field at 90° and 30° are also shown to manifest, respectively, high- and low-frequency wave-like motions when using a combination of only the low-order velocity modes (m=0, 1, 2). This work thus constitutes a first step in developing low-dimensional and dynamical system models from hydrodynamic pressure signatures for estimating and predicting the behaviour of the energy-containing events that govern many of the physical constituents of turbulent flows.

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26

Purushothaman, B. K., and J. S. Wainright. "Analysis of pressure variations in a low-pressure nickel–hydrogen battery. Part 2: Cells with metal hydride storage." Journal of Power Sources 206 (May 2012): 421–28. http://dx.doi.org/10.1016/j.jpowsour.2012.01.149.

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27

Amundsen, Lasse, and Hongbo Zhou. "Low-frequency seismic deghosting." GEOPHYSICS 78, no. 2 (March 1, 2013): WA15—WA20. http://dx.doi.org/10.1190/geo2012-0276.1.

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We evaluated a solution to seismic deghosting that deghosts the low-frequency components of the seismic pressure data. In an approximation that neglected the dependence on wavenumbers, the low-frequency deghosted pressure field was computed trace-by-trace as the sum of the pressure field and its scaled temporally integrated and temporally differentiated fields. We gave simple numerical examples that demonstrated the concept. The method was found to deghost data up to a frequency that is typically half of the second notch frequency. On the low-frequency side, the deghosting method was limited by the signal-to-noise ratio. The low-frequency deghosting technique can be appropriate to apply to the part of seismic data that have penetrated and reflected beneath complex and attenuating overburdens such as basalt, salt, and chalk.

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28

Chernoff, Don. "X-ray Analysis in the Low Vacuum SEM (Part 3 of 3)." Microscopy Today 6, no. 10 (December 1998): 10–13. http://dx.doi.org/10.1017/s1551929500069650.

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In this third and final installment on x-ray analysis in the environmental and low vacuum SEM, I will present experimental methods for measuring beam scatter. In my previous two articles I discussed how operating conditions detemine beam scatter. It was shown that the type of gas used, the gas pressure in the chamber, the working distance or beam gas path length, and the accelerating voltage all have an effect on how much the electron beam scatters. I also discussed how the beam scatter influences x-ray results by producing x-rays beyond the area of the primary beam. Furthermore, I showed how software models could be used to determine the amount of beam scatter based on different combinations of the four variables (pressure, gas, working distance, and kV).

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29

Zhang, T., and J. R. G. Evans. "The solidification of large sections in ceramic injection molding: Part II. Modulated pressure molding." Journal of Materials Research 8, no. 2 (February 1993): 345–51. http://dx.doi.org/10.1557/jmr.1993.0345.

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Cylindrical moldings of 20 and 40 mm diameter were injection molded with the application of modulated hold pressure using a well-characterized alumina-polypropylene suspension. The effect of frequency on sprue solidification was explored. For the smaller moldings, very little extension to sprue solidification time was obtained with pressures up to 140 MPa, and this is attributed to the low reciprocating volume flow. For the larger moldings, pressures of 98 MPa were sufficient to produce moldings with neither voids nor cracks, and the sprue solidification time corresponded to the time needed for solidification of the molding. The use of higher pressures resulted in internal residual stresses which were qualitatively detected by the defomation on annealing of polished diametral sections.

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30

Scapozza, Carlo, and Perry Bartelt. "Triaxial tests on snow at low strain rate. Part II. Constitutive behaviour." Journal of Glaciology 49, no. 164 (2003): 91–101. http://dx.doi.org/10.3189/172756503781830890.

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AbstractFine-grained, dry snow with a density range of 190–435 kg m−3 was tested in triaxial compression at −12°C with confining pressures varying between 0 and 40 kPa. The tests were strain-rate controlled, with strain rates ranging between 7.4 × 10−7 s−1 and 6.6 × 10−5 s−1. The analysis of the test results revealed that the relationship between yield stress and viscous strain rate is best given by a power law, similar to polycrystalline ice. However, the power-law exponent n is a function of density and varies between 1.8 (low-density snow, ρ < 200 kg m−3) and 3.6 (high-density snow, ρ > 320 kg m−3). The tests also showed that lower-density snow displays a significant non-linear stress–strain response before yielding. Two further aspects of the constitutive behaviour of snow were identified: (1) the strainrate independence of the post-yield work-hardening behaviour in compression and (2) the independence of the axial yield stress in relation to the confining pressure. The experimental observations are discussed with respect to the mechanical properties of polycrystalline ice, which is the constituent material of the load-bearing ice skeleton.

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31

Jianhui, Zhou, Haruhiko Ohya, and Takeshi Hino. "Reverse osmotic concentration of aqueous solution of low molecular weight organic solutes. Part II: Low pressure RO membranes." membrane 15, no. 5 (1990): 277–83. http://dx.doi.org/10.5360/membrane.15.277.

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32

Gonza´lez, P., I. Ulizar, R. Va´zquez, and H. P. Hodson. "Pressure and Suction Surfaces Redesign for High-Lift Low-Pressure Turbines." Journal of Turbomachinery 124, no. 2 (April 1, 2002): 161–66. http://dx.doi.org/10.1115/1.1452747.

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Nowadays there is a big effort toward improving the low-pressure turbine efficiency even to the extent of penalizing other relevant design parameters. LP turbine efficiency influences SFC more than other modules in the engine. Most of the research has been oriented to reduce profile losses, modifying the suction surface, the pressure surface, or the three-dimensional regions of the flow. To date, the pressure surface has received very little attention. The dependence of the profile losses on the behavior of both pressure and suction surfaces has been investigated for the case of a high-lift design that is representative of a modern civil engine LP turbine. The experimental work described in this paper consists of two different sets of experiments: the first one concluded an improved pressure surface definition, and the second set was oriented to achieve further improvement in losses modifying the profile suction surface. Three profiles were designed and tested over a range of conditions. The first profile is a thin-solid design. This profile has a large pressure side separation bubble extending from near the leading edge to midchord. The second profile is a hollow design with the same suction surface as the first one, but avoiding pressure surface separation. The third one is also a hollow design with the same pressure surface as the second profile, but more aft loaded suction surface. The study is part of a wider ongoing research program covering the effects of the different design parameters on losses. The paper describes the experiments conducted in a low-speed linear cascade facility. It gathers together steady and unsteady loss measurements by wake traverse and surface pressure distributions for all the profiles. It is shown that thick profiles generate only around 90 percent of the losses of a thin-solid profile with the same suction surface. The results support the idea of an optimum axial position for the peak Mach number. Caution is recommended, as profile aft loading would not be a completely secure method for reducing losses.

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33

Peslin, R., C. Duvivier, B. Suki, R. Farre, E. Oostveen, and C. Gallina. "Respiratory impedance to ambient pressure changes at low frequencies." Journal of Applied Physiology 68, no. 2 (February 1, 1990): 665–71. http://dx.doi.org/10.1152/jappl.1990.68.2.665.

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Respiratory impedance may be studied by measuring airway flow (Vaw) when pressure is varied at the mouth (input impedance) or around the chest (transfer impedance). A third possibility, which had not been investigated so far, is to apply pressure variations simultaneously at the two places, that is to vary ambient pressure (Pam). This provides respiratory impedance to ambient pressure changes (Zapc = Vaw/Pam). In that situation airway impedance (Zaw) and tissue impedance (Zt) are mechanically in parallel, and both are in series with alveolar gas impedance (Zg): Zapc = Zaw + Zg + Zaw.Zg/Zt. We assessed the frequency dependence of Zapc from 0.05 to 2 Hz in nine normal subjects submitted to sinusoidal Pam changes of 2-4 kPa peak to peak. The real part of Zapc (Rapc) was of 6.2 kPa.1(-1).s at 0.05 Hz and decreased to 1.9 kPa.1(-1).s at 2 Hz. Similarly the effective compliance (Capc), computed from the imaginary part of Zapc, decreased from 0.045 1.kPa-1 at 0.05 Hz to 0.027 1.kPa-1 at 2 Hz. Breathing against an added resistance of 0.46 kPa.1(-1).s exaggerated the negative frequency dependence of both Rapc and Capc. When values of airway resistance and inertance derived from transfer impedance data were introduced, Zapc was used to compute effective tissue resistance (Rt) and compliance (Ct). Rt was found to decrease from 0.32 to 0.15 kPa.1(-1).s and Ct from 1.11 to 0.64 1.kPa-1 between 0.25 and 2 Hz. Ct was slightly lower with the added resistance. These results are in good agreement with the data obtained by other approaches.

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34

Rubtsov, Nickolai M., Victor Chernysh, Georgiy Tsvetkov, Kirill Troshin, and Alexander Kalinin. "The features of hydrogen ignition over platinum-group metals at low pressure. Part. I." Physical-Chemical Kinetics in Gas Dynamics 19, no. 1 (March 6, 2018): 1–8. http://dx.doi.org/10.33257/phchgd.19.1.730.

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35

Kowalski, T. Z. "Gas gain limitation in low pressure proportional counters filled with TEG mixtures—part II." Journal of Instrumentation 11, no. 01 (January 19, 2016): P01009. http://dx.doi.org/10.1088/1748-0221/11/01/p01009.

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36

Meige, A., D. O'Connell, T. Gans, and R. W. Boswell. "Plasma Ionization in Low-Pressure Radio-Frequency Discharges—Part II: Particle-in-Cell Simulation." IEEE Transactions on Plasma Science 36, no. 4 (August 2008): 1384–85. http://dx.doi.org/10.1109/tps.2008.926833.

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37

Siboni, Anders H. "Old Pulmonary Embolus of the Distal Part of a Pudenz Low-Pressure Ventriculoatrial Shunt." American Journal of Forensic Medicine and Pathology 7, no. 1 (March 1986): 69–71. http://dx.doi.org/10.1097/00000433-198603000-00015.

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38

Hegemann, Dirk, Bernard Nisol, Sean Watson, and Michael R. Wertheimer. "Energy Conversion Efficiency in Low- and Atmospheric-Pressure Plasma Polymerization Processes, Part II: HMDSO." Plasma Chemistry and Plasma Processing 37, no. 1 (October 28, 2016): 257–71. http://dx.doi.org/10.1007/s11090-016-9754-x.

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39

Volino, Ralph J. "Separated Flow Transition Under Simulated Low-Pressure Turbine Airfoil Conditions—Part 2: Turbulence Spectra." Journal of Turbomachinery 124, no. 4 (October 1, 2002): 656–64. http://dx.doi.org/10.1115/1.1506939.

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Spectral analysis was used to investigate boundary layer separation, transition and reattachment under low-pressure turbine airfoil conditions. Cases with Reynolds numbers ranging from 25,000 to 300,000 (based on suction surface length and exit velocity) have been considered at low (0.5%) and high (9% inlet) free-stream turbulence levels. Spectra of the fluctuating streamwise velocity and the turbulent shear stress are presented. The spectra for the low free-stream turbulence cases are characterized by sharp peaks. The high free-stream turbulence case spectra exhibit more broadband peaks, but these peaks are centered at the same frequencies observed in the corresponding low turbulence cases. The frequencies of the peaks suggest that a Tollmien-Schlichting instability mechanism drives transition, even in the high turbulence cases. The turbulent shear stress spectra proved particularly valuable for detection of the early growth of the instability. The predictable nature of the instability may prove useful for future flow control work.

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40

Kumar, K. Suresh. "Modeling of wind-induced pressure fluctuations on roofs of low-rise buildings." Canadian Journal of Civil Engineering 26, no. 4 (August 1, 1999): 453–67. http://dx.doi.org/10.1139/l99-011.

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A systematic study on the modeling of wind-induced pressures on low building roofs with application to extreme value and fatigue analysis is described in this paper. Extensive wind tunnel measurements form a basis to carry out the modeling. Based on the Fourier representation of time series, a general approach for simulating Gaussian as well as non-Gaussian wind pressure fluctuations has been presented. Both Fourier amplitude and phase required for the simulations are modeled individually. A simple stochastic model is proposed for the generation of Fourier phase of non-Gaussian time series. An empirical model has been suggested for the synthetic generation of normalized spectra; synthetic spectra are utilized for the generation of Fourier amplitude part. Towards the generalization of the simulation scheme, the standard spectral shapes associated with various zones of each roof and their parameters are established. The efficiency of this simulation methodology is illustrated with several examples. Applications of the simulation methodology have also been discussed. The established simulation scheme can be used to generate fluctuating wind pressures on low building roofs in a generic fashion not only for the evaluation of extreme pressures but also for fatigue design purposes.Key words: low-rise building, modeling, roofs, wind pressure.

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41

He, Chuanjiu, Fred T. Davies, and Ronald Lacey. "(305) Influence of Hypobaria on Gas Exchange and Growth of Lettuce for Advanced Life Support Systems (ALS)." HortScience 40, no. 4 (July 2005): 1011B—1011. http://dx.doi.org/10.21273/hortsci.40.4.1011b.

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There are advantages in growing plants under hypobaric (reduced atmospheric pressure) conditions in biomass production for extraterrestrial base or space-flight environments. Elevated levels of the plant hormone ethylene occur in enclosed crop production systems and in space-flight environments—leading to adverse plant growth and sterility. Objectives of this research were to characterize the influence of hypobaria on growth and ethylene evolution of lettuce (Lactuca sativa L. cv. Buttercrunch). Growth was comparable in lettuce grown under low (25 kPa) and ambient (101 kPa) total gas pressures. However, tip burn occurred under ambient, but not low pressure—in part because of adverse ethylene levels. Under ambient pressure, there were higher CO2 assimilation rates and dark respiration rates (higher night consumption of metabolites) compared to low pressure. This could lead to greater growth (biomass production) of low pressure plants during longer crop production cycles.

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42

Petrovic, M., and W. Riess. "Off-design flow analysis of low-pressure steam turbines." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 211, no. 3 (May 1, 1997): 215–24. http://dx.doi.org/10.1243/0957650971537123.

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In this paper, a method for flow calculation in large steam turbines is presented. The method is based on the through-flow theory and the finite element procedure. It includes some extensions and improvements in the form of a new combination of loss correlation, radial distribution of losses and spanwise mixing, a new procedure for density calculation and an extension to encompass reverse meridional flow. The method is applied to the LP (low-pressure) part of a 165 MW steam turbine for which the flow field and performance over a wide range of mass flow and input pressure are calculated. The flow at far off-design loads, at which flow reversal behind the last stage occurs, and the last stage changes to ventilation are especially analysed. The comparison of numerical results with experimental data shows good correspondence.

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43

Liberati, João Franklin, Oscar O. Araujo Filho, Waldemar Alfredo Monteiro, Iara M. Esposito, Rejane A. Nogueira, and Francisco Ambrozio Filho. "Low-Pressure Injection Molding Processing of AISI T15 High Speed Steel Powders." Materials Science Forum 514-516 (May 2006): 569–73. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.569.

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Low-pressure powder injection molding was used to obtain AISI T15 high speed steel parts. The binders used were based on paraffin wax, low density polyethylene and stearic acid. The metals powders were characterized in terms of morphology, particle size distribution. The mixture was injected in the shape of square bar specimens to evaluate the performance of the injection in the green state, and then sintered. The samples were injected under the pressures of 0.4, 0.5 and 0.7MPa and at temperatures varying from 110 to 150°C aiming the optimization of the process. The results of the variation of injection pressure were evaluated by measuring the density of the green parts. Debinding was carried out in two steps: first, the molded part was immersed in heptane to remove the major component of the binder and then heated to remove the remaining binder. A second step debinding and sintering were performed in a single step. This procedure shortened considerably the debinding and sintering time.

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44

Ghent, E. D., J. Nicholls, P. S. Simony, J. H. Sevigny, and M. Z. Stout. "Hornblende geobarometry of the Nelson Batholith, southeastern British Columbia: tectonic implications." Canadian Journal of Earth Sciences 28, no. 12 (December 1, 1991): 1982–91. http://dx.doi.org/10.1139/e91-180.

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Hornblende geobarometry has been applied to granitic rocks of the Middle Jurassic Nelson Batholith, British Columbia, locally containing magmatic epidote. Geobarometry suggests equilibration pressures of less than 4.5 kbar (1 kbar = 0.1 GPa) in the northern part of the batholith, which lacks magmatic epidote. This part of the pluton shows clear magmatic intrusive relations, and the contact metamorphic rocks contain andalusite, which suggests that the equilibration and emplacement pressures are compatible.In the southern part of the batholith, granitic rocks containing magmatic epidote have equilibration pressures of 4.8–6.4 kbar. South and west of Nelson, there is a distinct contrast in pressure between the pluton and the country rock. Both the contact metamorphic rocks and the low-grade regional metamorphic rocks suggest pressures in the 2–3 kbar range.The pressure difference of about 2 kbar across the southwestern contact and the variation in pressure within the batholith can be explained by a model combining a late postequilibration upsurge (diapiric) of a deeper part of the pluton in the south, with a much later rotation and tilting of the batholith, associated with Eocene motion on the upper listric portion of the Slocan Lake Fault. The late diapiric (?) upsurge may account for the pressure contrast across the southwestern contact.

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45

Sun, Yupeng, Huiling Tai, Zhen Yuan, Zaihua Duan, Qi Huang, and Yadong Jiang. "A Facile Strategy for Low Young's Modulus PDMS Microbeads Enhanced Flexible Capacitive Pressure Sensors (Part. Part. Syst. Charact. 7/2021)." Particle & Particle Systems Characterization 38, no. 7 (July 2021): 2170016. http://dx.doi.org/10.1002/ppsc.202170016.

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46

Wang, YuanGang, Chul Jin Kim, Chae Hoon Sohn, and In-Seuck Jeung. "A Numerical Study on Pressure Variation in a Shock Tube by Changing the Diameter Ratio of Low-Pressure (Driven) to High-Pressure (Driver) Part." Journal of the Korean Society of Combustion 21, no. 4 (December 30, 2016): 16–22. http://dx.doi.org/10.15231/jksc.2016.21.4.016.

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47

GEMMA, Hiroshi, Chiaki OOGAKI, Masayuki FUKUSHIMA, Tadao YAMADA, and Yoshihiro NOSE. "Preservation of some tropical fruits with an apparatus of low pressure storage for practical use. Effect of low pressure storage on fruits and vegetables. Part I." NIPPON SHOKUHIN KOGYO GAKKAISHI 36, no. 6 (1989): 508–18. http://dx.doi.org/10.3136/nskkk1962.36.6_508.

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48

Zhao, Ming, and Philip H. Austin. "Life Cycle of Numerically Simulated Shallow Cumulus Clouds. Part II: Mixing Dynamics." Journal of the Atmospheric Sciences 62, no. 5 (May 1, 2005): 1291–310. http://dx.doi.org/10.1175/jas3415.1.

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Abstract This paper is the second in a two-part series in which life cycles of six numerically simulated shallow cumulus clouds are systematically examined. The six clouds, selected from a single realization of a large-eddy simulation, grow as a series of pulses/thermals detached from the subcloud layer. All six clouds exhibit a coherent vortical circulation and a low buoyancy, low velocity trailing wake. The ascending cloud top (ACT), which contains this vortical circulation, is associated with a dynamic perturbation pressure field with high pressure located at the ascending frontal cap and low pressure below and on the downshear side of the maximum updrafts. Examination of the thermodynamic and kinematic structure, together with passive tracer experiments, suggests that this vortical circulation is primarily responsible for mixing between cloud and environment. As the cloud ACTs rise through the sheared environment, the low pressure, vortical circulation, and mixing are all strongly enhanced on the downshear side and weakened on the upshear side. Collapse of the ACT also occurs on the downshear side, with subsequent thermals ascending on the upshear side of their predecessors. The coherent core structure is maintained throughout the ACT ascent; mixing begins to gradually dilute the ACT core only in the upper half of the cloud's depth. The characteristic kinematic and dynamic structure of these simulated ACTs, together with their mixing behavior, corresponds closely to that of shedding thermals. These shallow simulated clouds, however, reach a maximum height of only about four ACT diameters so that ACT mixing differs from predictions of self-similar laboratory thermals.

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49

Xu, Ren. "Autostoichiometric vapor deposition: Part I. Theory." Journal of Materials Research 10, no. 10 (October 1995): 2536–41. http://dx.doi.org/10.1557/jmr.1995.2536.

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The possibility of an autostoichiometric vapor deposition is explored. Heterometal-organic complexes such as double alkoxides are potential candidate precursors for such deposition. Two reaction schemes, the hydrolysis-assisted pyrolysis and the hydrolysis-polycondensation of double alkoxides, are identified to be autostoichiometric reactions. A simple low-pressure apparatus is suggested for autostoichiometric vapor deposition. Mass-flow analysis allows for the identification of a nonstoichiometry factor K which can be used as a quantitative measure of the precursor's autostoichiometric capability.

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50

Rinas, Martin, Alexander Fricke, Jens Tränckner, Kurt Frischmuth, and Thilo Koegst. "Sediment Transport in Sewage Pressure Pipes, Part II: 1 D Numerical Simulation." Water 12, no. 1 (January 18, 2020): 282. http://dx.doi.org/10.3390/w12010282.

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Urban drainage modelling is a state-of-the-art tool to understand urban water cycles. Nevertheless, there are gaps in knowledge of urban water modelling. In particular pressure drainage systems are hardly considered in the scientific investigation of urban drainage systems, although they represent an important link in its network structure. This work is the conclusion of a series of investigations that have dealt intensively with pressure drainage systems. In particular, this involves the transport of sediments in pressure pipes. In a real-world case study, sediment transport inside a pressure pipe in an urban region in northern Germany was monitored by online total suspended solids measurements. This in situ data is used in this study for the development and calibration of a sediment transport model. The model is applied to investigate sediments transport under low flow velocities (due to energy saving intentions). The resulting simulation over 30 days pumping operation shows that a transport of sediments even at very low flow velocities of 0.27 m/s and under various inflow conditions (dry weather and storm water inflow) is feasible. Hence, with the help of the presented sediment transport model, energy-efficient pump controls can be developed without increasing the risk of deposition formation.

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