Journal articles on the topic 'Three-hole Probes'
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1
Sitaram, N., and A. L. Treaster. "A Simplified Method of Using Four-Hole Probes to Measure Three-Dimensional Flow Fields." Journal of Fluids Engineering 107, no. 1 (March 1, 1985): 31–35. http://dx.doi.org/10.1115/1.3242436.
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A simplified method of using four-hole probes to measure three-dimensional flow-fields is presented. This method is similar to an existing calibration and application procedure used for five-hole probes. The new method is demonstrated for two four-hole probes of different geometry. These four-hole probes and a five-hole probe are used to measure the turbulent boundary layer on a flat plate. The results from the three probes are in good agreement with theoretical predictions. The major discrepancies occur near the surface of the flat plate and are attributed to wall vicinity and velocity gradient effects.
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Cull, James, and Duncan Massie. "Noise Reduction for Down-hole Three-component TEM probes." ASEG Extended Abstracts 2001, no. 1 (December 2001): 1–3. http://dx.doi.org/10.1071/aseg2001ab027.
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Sitaram, Nekkanti, and Kancherla Srikanth. "Effect of Chamfer Angle on the Calibration Curves of Five Hole Probes." International Journal of Rotating Machinery 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/704315.
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Five hole probes are extensively used for measurement of total and static pressures, flow angles, velocity and its components in turbomachinery, and other aerodynamic flows. Their operating range is usually limited to 30–40° depending on the type of the probe head. The chamfer angle of the probe is usually taken around 45°. Recent studies on three hole probes have shown that 30° chamfer angle is desirable for unsteady flow measurements. Hence the present investigation is undertaken to find the optimum chamfer angle of five-hole probes. A special five-hole probe of 9.6 mm head diameter and 3 mm diameter pressure take off tubes was designed and fabricated. The large size of the probe was chosen to minimize machining inaccuracies. The probe chamfer angle was varied from 30° to 60° in 5° steps. For each of the chamfer angles, the probe was calibrated in the range of −30° to +30° in 5° interval and the calibration curves are presented. In addition the sensitivities of the calibration coefficients are determined. It is concluded that five-hole probe with a chamfer angle 30° has large operating range, while five-hole probe with a chamfer angle of 50° has good sensitivity.
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Argüelles Díaz, K. M., J. M. Fernández Oro, E. Blanco Marigorta, and R. Barrio Perotti. "Head geometry effects on pneumatic three-hole pressure probes for wide angular range." Flow Measurement and Instrumentation 21, no. 3 (September 2010): 330–39. http://dx.doi.org/10.1016/j.flowmeasinst.2010.04.004.
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Khalil, M. B., and E. G. Plett. "Measurement of Temperature and Velocity Vectors in a Combusting Environment Using Low-Cost Probes." Journal of Engineering for Gas Turbines and Power 110, no. 4 (October 1, 1988): 695–703. http://dx.doi.org/10.1115/1.3240194.
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Radial traverses were made to measure temperature distributions and velocity vectors in an atmospheric pressure test combustor burning gaseous fuels with heating values in the low-medium range. Temperature was measured using an aspirated pyrometer probe. Velocity vectors were determined from measurements of a five-hole probe (a two-hole probe was used prior to the five-hole probe to determine whether the flow was directed upstream or downstream). The measuring traverse was carried out across the entire diameter at ten sections along the combustor (which was specially designed to allow in insertion of probes at the ten axial sections, through three holes at 120 deg from each other around the circumference). These measurements were repeated for ten runs that incorporated a variety of operating conditions of the combustor. Temperature measurements were validated by application of the first law of thermodynamics. Velocities were validated using the principles of conservation of mass and angular momentum. The analysis showed that temperatures can be measured to within 10°C in a combusting environment of gaseous fuels for which the temperature is in the vicinity of 1500 K, by an aspirated pyrometer. The axial velocity component can be measured to an average accuracy of 7.6 percent using five-hole probes. The radial component of velocity can be obtained within ± 5 percent in most of the combustion space. The accuracy of measuring the circumferential velocity component could not be validated, partly because it was extremely small. Also, in order to validate it, some independent means of establishing its origin is needed. In this case, due to the lack of precision in fabricating the combustor and the holes for air admission, as well as due to the extremely small value of this component in the present study, it was not possible to establish the reliability of the measured values. The study recommends the use of aspirated pyrometers and five-hole probes in a combusting environment, provided that the yaw angle does not exceed 60 deg and the three components of velocity have comparable magnitudes. The probes should be made as small as possible and frequent purging should be practiced in their operation to avoid errors due to blockage of probes’ passages by water or dust particles. These probes were chosen for this application because of the ease with which they can be used, as well as for cost considerations.
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Dominy, R. G., and H. P. Hodson. "An Investigation of Factors Influencing the Calibration of Five-Hole Probes for Three-Dimensional Flow Measurements." Journal of Turbomachinery 115, no. 3 (July 1, 1993): 513–19. http://dx.doi.org/10.1115/1.2929281.
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The effects of Reynolds number, Mach number, and turbulence on the calibrations of commonly used types of five-hole probe are discussed. The majority of the probes were calibrated at the exit from a transonic nozzle over a range of Reynolds numbers (7 × 103 < Re < 80 × 103 based on probe tip diameter) at subsonic and transonic Mach numbers. Additional information relating to the flow structure were obtained from a large-scale, low-speed wind tunnel. The results confirmed the existence of two distinct Reynolds number effects. Flow separation around the probe head affects the calibrations at relatively low Reynolds numbers while changes in the detailed structure of the flow around the sensing holes affects the calibrations even when the probe is nulled. Compressibility is shown to have little influence upon the general behavior of these probes in terms of Reynolds number sensitivity but turbulence can affect the reliability of probe calibrations at typical test Reynolds numbers.
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Yao, Tao, Shudao Zhou, and Song Ye. "Design and Test of an Integrated Measurement System for Multi-Hole Probe Calibration and Vortex Measurement." Sensors 22, no. 6 (March 19, 2022): 2376. http://dx.doi.org/10.3390/s22062376.
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Multi-hole probes can simultaneously measure the velocity and direction of a flow field, obtain the distribution of the flow field in a three-dimensional space, and obtain the vortex information in the flow field. Moreover, a multi-hole probe needs to be calibrated while in use; therefore, a three-coordinate, multi-directional rotatable testing system, which can measure the flow field at any position and at any angle, was designed herein. A hemispherical seven-hole probe was calibrated with this test system, and the flow field around cylinders of different diameters was measured to obtain the pressure distribution and vortex shedding frequency. Furthermore, the designed test system’s ability to perform a multi-angle and multi-azimuth testing during the calibration of a multi-hole probe was verified. Simultaneously, through data mining of the multi-hole probe, vortices were measured, and periodic vortices were detected.
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Harrison, S. "Secondary Loss Generation in a Linear Cascade of High-Turning Turbine Blades." Journal of Turbomachinery 112, no. 4 (October 1, 1990): 618–24. http://dx.doi.org/10.1115/1.2927702.
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Flow through a linear cascade of high-turning, low aspect ratio turbine blades has been measured in great detail at five planes within the cascade and two downstream in order to trace the generation of stagnation pressure loss in the passage. Five-hole probes were used in the main flow, but as it is important to resolve the boundary layers accurately, three-hole and single flattened probes were used near the endwall and blade surfaces, respectively. Endwall shear stresses have been measured using a hot-film probe and an oil-drop viscosity balance technique. Numerical predictions and simple aerodynamic models are used in conjunction with the experimental data to estimate the relative importance of different loss mechanisms, including boundary layer shear stresses and mixing processes.
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Harada, H. "Performance Characteristics of Two- and Three-Dimensional Impellers in Centrifugal Compressors." Journal of Turbomachinery 110, no. 1 (January 1, 1988): 110–14. http://dx.doi.org/10.1115/1.3262155.
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The overall performance of two- and three-dimensional impellers of a centrifugal compressor were tested and compared. A closed-loop test stand with Freon gas as the working fluid was employed for the experiments. The inlet and outlet velocity distributions of all impellers were measured using three-hole cobra probes. As a result, it has been revealed that three-dimensional impeller in terms of efficiency, head coefficient, and operating range. Further, it has also been clarified that the impeller slip factor is affected by blade angle distribution.
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Coldrick, Simon, Paul Ivey, and Roger Wells. "Considerations for Using 3-D Pneumatic Probes in High-Speed Axial Compressors." Journal of Turbomachinery 125, no. 1 (January 1, 2003): 149–54. http://dx.doi.org/10.1115/1.1515334.
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This paper describes preparatory work towards three-dimensional flowfield measurements downstream of the rotor in an industrial, multistage, axial compressor, using a pneumatic pressure probe. The probe is of the steady-state four-hole cobra probe type. The design manufacture and calibration of the probe is described. CFD calculations have been undertaken in order to assess the feasibility of using such a probe in the high-speed compressor environment where space is limited. This includes effects of mounting the probe in close proximity to the downstream stator blades and whether it is necessary to adjust the calibration data to compensate for these effects.
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Smeets, C. J. P. P., W. Boot, A. Hubbard, R. Pettersson, F. Wilhelms, M. R. Van Den Broeke, and R. S. W. Van De Wal. "A wireless subglacial probe for deep ice applications." Journal of Glaciology 58, no. 211 (2012): 841–48. http://dx.doi.org/10.3189/2012jog11j130.
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AbstractWe present the design and first results from two experiments using a wireless subglacial sensor system (WiSe) that is able to transmit data through 2500 m thick ice. Energy consumption of the probes is minimized, enabling the transmission of data for at least 10 years. In July 2010 the first prototype of the system was used to measure subglacial pressure at the base and a temperature profile consisting of 23 probes in two 600 m deep holes at Russell Glacier, a land-terminating part of the West Greenland ice sheet near Kangerlussuaq. The time series of subglacial pressure show very good agreement between data from the WiSe system and the wired reference system. The wireless-measured temperature data were validated by comparison with the theoretical decrease of melting point with water pressure inside the water-filled hole directly after installation. To test the depth range of the WiSe system a second experiment using three different probe types and two different surface antennas was performed inside the 2537 m deep hole at NEEM. It is demonstrated that, with the proper combination of transmission power and surface antenna type, the WiSe system transmits data through 2500 m thick ice.
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Wong, Thomas Hong Tsun, Hugo Pfister, and Lixin Dai. "Revisiting the Rates and Demographics of Tidal Disruption Events: Effects of the Disk Formation Efficiency." Astrophysical Journal Letters 927, no. 1 (March 1, 2022): L19. http://dx.doi.org/10.3847/2041-8213/ac5823.
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Abstract Tidal disruption events (TDEs) are valuable probes of the demographics of supermassive black holes as well as the dynamics and population of stars in the centers of galaxies. In this Letter, we focus on studying how debris disk formation and circularization processes can impact the possibility of observing prompt flares in TDEs. First, we investigate how the efficiency of disk formation is determined by the key parameters, namely, the black hole mass M BH, the stellar mass m ⋆, and the orbital penetration parameter β that quantifies how close the disrupted star would orbit around the black hole. Then we calculate the intrinsic differential TDE rate as a function of these three parameters. Combining these two results, we find that the rates of TDEs with prompt disk formation are significantly suppressed around lighter black holes, which provides a plausible explanation for why the observed TDE host black hole mass distribution peaks between 106 and 107 M ⊙. Therefore, the consideration of disk formation efficiency is crucial for recovering the intrinsic black hole demographics from TDEs. Furthermore, we find that the efficiency of the disk formation process also impacts the distributions of both stellar orbital penetration parameter and stellar mass observed in TDEs.
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Smout, P. D., and P. C. Ivey. "Investigation of Wedge Probe Wall Proximity Effects: Part 1—Experimental Study." Journal of Engineering for Gas Turbines and Power 119, no. 3 (July 1, 1997): 598–604. http://dx.doi.org/10.1115/1.2817026.
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Conventional three-hole wedge probes fail to measure the correct static pressure when operating in close proximity to a wall or boundary through which the probe is inserted. The free-stream pressure near the outer wall of a turbomachine may be overindicated by up to 20 percent dynamic head. This paper reports a series of experiments aimed at quantifying this so-called “wall proximity effect.” It is shown from a factorial experiment that probe wedge angle, stem design, and free-stream Mach number all have a significant influence. The yaw angle sensitivity of wedge probes is also found to depend on the proximity of the probe to the wall of introduction. Flow visualization studies on large-scale probe models are described, and a qualitative model of the probe local flow structures is developed. This model is used to explain the near-wall characteristics of the actual size wedge probes. In Part 2 of this paper, the experimental data are used to validate CFD calculations of the flow field around a wedge probe. A simple analytical model of the probe/flow interaction is developed from the CFD solutions.
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Green, Sheldon I., and Steven N. Rogak. "A Multiple Disk Probe for Inexpensive and Robust Velocimetry." Journal of Fluids Engineering 121, no. 2 (June 1, 1999): 446–49. http://dx.doi.org/10.1115/1.2822230.
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A novel velocimeter consisting of multiple orthogonal disks fitted with pressure transducers has been developed. Dynamic pressure differences are measured between the center of one disk face and the center of the other face, on each of the disks. While previously-developed anemometers based on dynamic pressure differences (such as yaw or three-hole probes) can only measure velocities with a small range of directions, the new disk probe can measure three components of velocity, even in highly three-dimensional flows where the approximate direction of the flow is not known. Wind tunnel tests have shown the velocimeter to be quite accurate; it can measure velocities to ±1.4% and wind directions to ±4 deg. The velocimeter is very robust and therefore can make measurements in environments too harsh for most other velocity transducers.
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Moore, J., and R. Y. Adhye. "Secondary Flows and Losses Downstream of a Turbine Cascade." Journal of Engineering for Gas Turbines and Power 107, no. 4 (October 1, 1985): 961–68. http://dx.doi.org/10.1115/1.3239842.
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The loss mechanisms and the behavior of secondary flows downstream of a large scale, linear turbine cascade have been investigated experimentally. A five-blade replica of the cascade used by Langston et al. at United Technologies Research Center was used for the present tests. Detailed flow measurements, using five-hole and three-hole probes, were made at four different planes, one just upstream of the trailing edge and the rest downstream. The secondary flow field at each measurement plane was found to be dominated by a single large passage vortex, which decayed in strength because of the mixing occurring in the flow. More than one-third of the losses were found to occur downstream of the trailing edge. This rise in total pressure loss in the present tests was almost entirely explained by a corresponding dissipation of the secondary kinetic energy of the flow. A mixing analysis of the flow was done to predict the additional losses due to “mixing” until the flow became completely uniform.
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Wang, Jinhua, Pan Nie, Xiaokang Li, Huakun Zuo, Benoît Fauqué, Zengwei Zhu, and Kamran Behnia. "Critical point for Bose–Einstein condensation of excitons in graphite." Proceedings of the National Academy of Sciences 117, no. 48 (November 16, 2020): 30215–19. http://dx.doi.org/10.1073/pnas.2012811117.
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An exciton is an electron–hole pair bound by attractive Coulomb interaction. Short-lived excitons have been detected by a variety of experimental probes in numerous contexts. An excitonic insulator, a collective state of such excitons, has been more elusive. Here, thanks to Nernst measurements in pulsed magnetic fields, we show that in graphite there is a critical temperature (T = 9.2 K) and a critical magnetic field (B = 47 T) for Bose–Einstein condensation of excitons. At this critical field, hole and electron Landau subbands simultaneously cross the Fermi level and allow exciton formation. By quantifying the effective mass and the spatial separation of the excitons in the basal plane, we show that the degeneracy temperature of the excitonic fluid corresponds to this critical temperature. This identification would explain why the field-induced transition observed in graphite is not a universal feature of three-dimensional electron systems pushed beyond the quantum limit.
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Rautenberg, Alexander, Jonas Allgeier, Saskia Jung, and Jens Bange. "Calibration Procedure and Accuracy of Wind and Turbulence Measurements with Five-Hole Probes on Fixed-Wing Unmanned Aircraft in the Atmospheric Boundary Layer and Wind Turbine Wakes." Atmosphere 10, no. 3 (March 7, 2019): 124. http://dx.doi.org/10.3390/atmos10030124.
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For research in the atmospheric boundary layer and in the vicinity of wind turbines, the turbulent 3D wind vector can be measured from fixed-wing unmanned aerial systems (UAS) with a five-hole probe and an inertial navigation system. Since non-zero vertical wind and varying horizontal wind causes variations in the airspeed of the UAS, and since it is desirable to sample with a flexible cruising airspeed to match a broad range of operational requirements, the influence of airspeed variations on mean values and turbulence statistics is investigated. Three calibrations of the five-hole probe at three different airspeeds are applied to the data of three flight experiments. Mean values and statistical moments of second order, calculated from horizontal straight level flights are compared between flights in a stably stratified polar boundary layer and flights over complex terrain in high turbulence. Mean values are robust against airspeed variations, but the turbulent kinetic energy, variances and especially covariances, and the integral length scale are strongly influenced. Furthermore, a transect through the wake of a wind turbine and a tip vortex is analyzed, showing the instantaneous influence of the intense variations of the airspeed on the measurement of the turbulent 3D wind vector. For turbulence statistics, flux calculations, and quantitative analysis of turbine wake characteristics, an independent measurement of the true airspeed with a pitot tube and the interpolation of calibration polynomials at different Reynolds numbers of the probe’s tip onto the Reynolds number during the measurement, reducing the uncertainty significantly.
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Go¨ttlich, E., F. Neumayer, J. Woisetschla¨ger, W. Sanz, and F. Heitmeir. "Investigation of Stator-Rotor Interaction in a Transonic Turbine Stage Using Laser Doppler Velocimetry and Pneumatic Probes." Journal of Turbomachinery 126, no. 2 (April 1, 2004): 297–305. http://dx.doi.org/10.1115/1.1649745.
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The current paper presents steady and unsteady flow data of a transonic test turbine stage operating under flow conditions similar to modern highly loaded gas turbines. Measurements were performed between stator and rotor as well as downstream of the rotor in planes perpendicular to the rotor axis. Time-resolved axial and tangential velocities were measured by a two-component laser doppler velocimeter (LDV) to investigate unsteady phenomena, while time-averaged flow properties were measured by means of a pneumatic seven-hole probe for all three spatial directions. The time-resolved investigation done by LDV allows to present velocity fields, flow angles and turbulence data at different stator-rotor positions during one blade passing period. Averaging these results enabled comparison with the pneumatic multihole probe measurement. LDV data and stage geometry can be obtained per email request and used for computational fluid dynamics (CFD) code verification.
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Calmer, Radiance, Gregory C. Roberts, Jana Preissler, Kevin J. Sanchez, Solène Derrien, and Colin O'Dowd. "Vertical wind velocity measurements using a five-hole probe with remotely piloted aircraft to study aerosol–cloud interactions." Atmospheric Measurement Techniques 11, no. 5 (May 3, 2018): 2583–99. http://dx.doi.org/10.5194/amt-11-2583-2018.
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Abstract. The importance of vertical wind velocities (in particular positive vertical wind velocities or updrafts) in atmospheric science has motivated the need to deploy multi-hole probes developed for manned aircraft in small remotely piloted aircraft (RPA). In atmospheric research, lightweight RPAs (< 2.5 kg) are now able to accurately measure atmospheric wind vectors, even in a cloud, which provides essential observing tools for understanding aerosol–cloud interactions. The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) focuses on these specific interactions. In particular, vertical wind velocity at cloud base is a key parameter for studying aerosol–cloud interactions. To measure the three components of wind, a RPA is equipped with a five-hole probe, pressure sensors, and an inertial navigation system (INS). The five-hole probe is calibrated on a multi-axis platform, and the probe–INS system is validated in a wind tunnel. Once mounted on a RPA, power spectral density (PSD) functions and turbulent kinetic energy (TKE) derived from the five-hole probe are compared with sonic anemometers on a meteorological mast. During a BACCHUS field campaign at Mace Head Atmospheric Research Station (Ireland), a fleet of RPAs was deployed to profile the atmosphere and complement ground-based and satellite observations of physical and chemical properties of aerosols, clouds, and meteorological state parameters. The five-hole probe was flown on straight-and-level legs to measure vertical wind velocities within clouds. The vertical velocity measurements from the RPA are validated with vertical velocities derived from a ground-based cloud radar by showing that both measurements yield model-simulated cloud droplet number concentrations within 10 %. The updraft velocity distributions illustrate distinct relationships between vertical cloud fields in different meteorological conditions.
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Thiago de Souza, Carnavale, Campos Tácio Mauro Pereira de, and Lopes Haimon Diniz Alves. "Evaluation of installation procedures of volumetric water content and matric potential probes: fundamentals for obtaining field and laboratory accordance." MATEC Web of Conferences 337 (2021): 01009. http://dx.doi.org/10.1051/matecconf/202133701009.
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The current paper aims to analyze the influence of installation procedures when it comes to the accordance of the Soil Water Retention Curve and field monitoring data. The method comprises testing three different installation procedures: with driving the rod into the soil; with the application of mud inside the auger hole; and with a hardened steel gauge. Further, is evaluated the influence of the variation of Bulk density on volumetric water content values by using the Proctor and a double ring hydraulic equipment. To analyze the soil-rod coupling, a microtomography imaging routine was performed. The results point out that the probe’s data are connected to the Bulk density of the material, producing higher volumetric water content values with the increase of Bulk density. Comparing results of different installation methods with laboratory results, it is possible to conclude that driving the rod directly into the soil is the best way to install the equipment since the probe underestimates the volumetric water content data by 2,5%, while the mud application by 4%, and the gauge method by 5%.
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Snyder, Donald D., and David B. Fleming. "Well logging—A 25‐year perspective." GEOPHYSICS 50, no. 12 (December 1985): 2504–29. http://dx.doi.org/10.1190/1.1441881.
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Developments in the field of well logging over the last 25 years are reviewed. Surface and borehole instrumentation have evolved significantly, taking advantage of modern digital and analog integrated circuits. Most open‐hole petroleum well logs are now recorded digitally. Digital logs are also frequently acquired in cased‐hole petroleum, mineral, and geotechnical applications. Nuclear well‐log measurements have become accepted and reliable. New measurements include borehole compensated density and neutron‐porosity, sidewall epithermal neutron‐porosity, and most recently litho‐density. The neutron decay log, developed early in the 25‐year period, has undergone a number of major improvements since its introduction. Probes which make spectral measurements of natural gamma‐ray emission, and gamma‐ray emission from neutron interactions with matter have also been developed. Resistivity measurements are now made with probes which combine three or more sensors each with different depths of investigation so that information about the borehole invasion profile can be acquired. Acoustic logging methods have expressed major developments and improvements. The compensated sonic measurement was introduced early in the period along with the cement bond logging method. Interest in measurement of shear‐wave velocity has produced new direct shear‐wave measurements as well as improved acoustic probes for full‐waveform acoustic logging. Other interesting or promising methods which have been developed or improved during the period include the borehole televiewer, the borehole gravimeter, and the nuclear magnetic resonance log. The digital computer provides powerful capabilities for well‐log analysis both at the well site and in the office. Analysis of complex sand‐shale and carbonate formations using two or more logs in a simultaneous solution of a litho‐porosity model is now routine. Powerful signal processing techniques are being applied to “deconvolve” well logs, to enhance or synthesize images of the wellbore, and to estimate or extract information from full‐waveform acoustic logs. While new or improved measurements have been introduced and log analysts now have access to powerful computers and graphic work stations, understanding of the petrophysical significance of the measurements lags behind the basic hardware measurement and interpretation technology.
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Behr, T., L. Porreca, T. Mokulys, A. I. Kalfas, and R. S. Abhari. "Multistage Aspects and Unsteady Effects of Stator and Rotor Clocking in an Axial Turbine With Low Aspect Ratio Blading." Journal of Turbomachinery 128, no. 1 (June 28, 2005): 11–22. http://dx.doi.org/10.1115/1.2101855.
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This paper presents the outcome of a recent study in clocking-related flow features and multistage effects occurring in high-pressure turbine blade geometries. The current investigation deals with an experimentally based systematic analysis of the effects of both stator-stator and rotor-rotor clocking. Due to the low aspect ratio of the turbine geometry, the flow field is strongly three-dimensional and is dominated by secondary flow structures. The investigation aims to identify the flow interactions involved and the associated effects on performance improvement or degradation. Consequently a three-dimensional numerical analysis has been undertaken to provide the numerical background to the test case considered. The experimental studies were performed in a two-stage axial research turbine facility. The turbine provides a realistic multi-stage environment, in which both stator blade rows and the two rotors can be clocked relative to each other. All blade rows have the same blade number count, which tends to amplify clocking effects. Unsteady and steady measurements were obtained in the second stage using fast response aerodynamic probes and miniature pneumatic five-hole probes. The current comprehensive investigation has shown that multistage and unsteady flow effects of stator and rotor clocking in low aspect ratio turbines are combined in a nonlinear fashion caused by axial and radial redistribution of low energy fluid. The integral result of clocking on stage efficiency is compensated by competing loss generating mechanisms across the span.
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Wanjin, Han, Wang Zhongqi, Tan Chunqing, Shi Hong, and Zhou Mochun. "Effects of Leaning and Curving of Blades With High Turning Angles on the Aerodynamic Characteristics of Turbine Rectangular Cascades." Journal of Turbomachinery 116, no. 3 (July 1, 1994): 417–24. http://dx.doi.org/10.1115/1.2929428.
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To understand the effects of the origination and development of centralized vortices on the aerodynamic characteristics of turbine rectangular cascades with high turning angles, experiments with five-hole microspherical probes, accompanied by color helium bubble flow displays, were carried out. The measurement planes are arranged as three before, six in, and one after the cascade. The experiments reveal that the origination and development of horseshoe vortices and passage vortices as well as the interaction of the latters almost dominate the whole flow field of traditional linear cascades. Lean linear cascades favor the horseshoe vortices and passage vortices in the acute angle zone, and impede those in the obtuse angle zone. So it is a logical result to adopt the negatively curved blades, whose pressure surfaces and both endwalls compose both obtuse angles, respectively, to improve the cascade aerodynamic characteristics.
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Kim, Wu J., and Virendra C. Patel. "Origin and Decay of Longitudinal Vortices in Developing Flow in a Curved Rectangular Duct (Data Bank Contribution)." Journal of Fluids Engineering 116, no. 1 (March 1, 1994): 45–52. http://dx.doi.org/10.1115/1.2910240.
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Developing turbulent flow in a 90 deg curved duct of rectangular cross-section, and an aspect ratio of 6, was investigated. Mean-velocity and Reynolds-stress components were measured using a five-hole pressure probe and two-sensor hot-wire probes, respectively, in the boundary layers on the duct walls to document the pressure-driven secondary motion and the formation of a longitudinal vortex near the corner on the convex wall. Special attention was paid to the three-dimensionality of the flow exiting the two-dimensional contraction of the wind tunnel in order to provide proper inlet boundary conditions for future computational work. The mean velocities and wall shear stresses were measured at seven sections and turbulence measurement were made at four sections. The data provide insights into the development of three-dimensional turbulent boundary layers under the influence of strong streamwise curvature, both convex or concave, and attendant pressure gradients, and clearly elucidate the mechanism by which strong pressure-driven secondary motion results in a longitudinal vortex.
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Boletis, E. "Effects of Tip Endwall Contouring on the Three-Dimensional Flow Field in an Annular Turbine Nozzle Guide Vane: Part 1—Experimental Investigation." Journal of Engineering for Gas Turbines and Power 107, no. 4 (October 1, 1985): 983–90. http://dx.doi.org/10.1115/1.3239845.
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Tip endwall contouring is one of the most effective methods to improve the performance of low aspect ratio turbine vanes [1]. In view of the wide variety of geometric parameters, it appears that only the physical understanding of the three-dimensional flow field will allow us to evaluate the probable benefits of a particular endwall contouring. The paper describes the experimental investigation of the three-dimensional flow through a low-speed, low aspect ratio, high-turning annular turbine nozzle guide vane with meridional tip endwall contouring. The full impact of the effects of tip contouring is evaluated by comparison with the results of a previous study in an annular turbine nozzle guide vane of the same blade and cascade geometry with cylindrical endwalls [12]. In parallel, the present experimental study provides a fully three-dimensional test case for comparison with advanced theoretical calculation methods [15]. The flow is explored by means of double-head, four-hole pressure probes in five axial planes from far upstream to downstream of the blade row. The results are presented in the form of contour plots and spanwise pitch-averaged distributions.
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Benner, M. W., S. A. Sjolander, and S. H. Moustapha. "The Influence of Leading-Edge Geometry on Secondary Losses in a Turbine Cascade at the Design Incidence." Journal of Turbomachinery 126, no. 2 (April 1, 2004): 277–87. http://dx.doi.org/10.1115/1.1645533.
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The paper presents detailed experimental results of the secondary flows from two large-scale, low-speed linear turbine cascades. The aerofoils for the two cascades were designed for the same inlet and outlet conditions and differ mainly in their leading-edge geometries. Detailed flow field measurements were made upstream and downstream of the cascades using three and seven-hole pressure probes and static pressure distributions were measured on the aerofoil surfaces. All measurements were made exclusively at the design incidence. The results from this experiment suggest that the strength of the passage vortex plays an important role in the downstream flow field and loss behavior. It was concluded that the aerofoil loading distribution has a significant influence on the strength of this vortex. In contrast, the leading-edge geometry appears to have only a minor influence on the secondary flow field, at least for the design incidence.
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Carrillo, Joseph D., Joey S. Mayorquin, Jason E. Stajich, and Akif Eskalen. "Probe-Based Multiplex Real-Time PCR as a Diagnostic Tool to Distinguish Distinct Fungal Symbionts Associated With Euwallacea kuroshio and Euwallacea whitfordiodendrus in California." Plant Disease 104, no. 1 (January 2020): 227–38. http://dx.doi.org/10.1094/pdis-01-19-0201-re.
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California has been invaded by two distinct Euwallacea spp. that vector unique plant pathogenic symbiotic fungi on multiple hosts and cause Fusarium dieback. The objective of this study was to develop multiplex real-time quantitative PCR assays using hydrolysis probes targeting the β-tubulin gene to detect, distinguish, and quantify fungi associated with the polyphagous shot hole borer (PSHB; Euwallacea whitfordiodendrus, Fusarium euwallaceae, Graphium euwallaceae, and Paracremonium pembeum) as well as the Kuroshio shot hole borer (KSHB; Euwallacea kuroshio, Fusarium kuroshium, and Graphium kuroshium) from various sample types. Absolute quantification reaction efficiencies ranged from 88.2 to 104.3%, with a coefficient of determination >0.992 and a limit of detection of 100 copies µl−1 for all targets across both assays. Qualitative detection using the real-time assays on artificially inoculated avocado shoot extracts showed more sensitivity compared with conventional fungal isolation from wood. All symbiotic fungi, except P. pembeum, from PSHB and KSHB female heads were detectable and quantified. Field samples from symptomatic Platanus racemosa, Populus spp., and Salix spp. across 17 of 26 city parks were positively identified as PSHB and KSHB through detection of their symbiotic fungi, and both were found occurring together on five trees from three different park locations. The molecular assays presented here can be utilized to accurately identify fungi associated with these invasive pests in California.
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Pfau, Axel, Joel Schlienger, Anestis I. Kalfas, and Reza S. Abhari. "Virtual four sensor fast response aerodynamic probe (FRAP®)." E3S Web of Conferences 345 (2022): 01014. http://dx.doi.org/10.1051/e3sconf/202234501014.
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This paper introduces the new fast response aerodynamic probe (FRAP®), which was recently developed at the ETH Zurich. The probe provides time-resolved, three-dimensional flow measurements using the virtual four sensor technique. Two probes work in tandem, being comparable to a pair of pneumatic needle probes. The first probe, being yaw angle sensitive, is positioned in three circumferential positions. The second probe being pitch angle sensitive is brought into exactly the same position as the first probe. The resulting set of four measurements is phaselock-averaged to one specific rotor trigger position. Then the reduced data sets are combined to four calibration coefficients, which are then further processed to determine the unsteady flow vector. The results consist of yaw and pitch flow angles as well as the total and static pressure. The outer diameter of the cylindrical probe head was miniaturized to 0.84mm, hence probe blockage effects as well as dynamic lift effects are reduced. The shape of the probe head was optimized in view of the manufacturing process as well as aerodynamic considerations. The optimum geometry for pitch sensitivity was found to be a cylindrical surface with the axis perpendicular to the probe shaft. The internal design of the probes led to a sensor cavity eigen frequency of 44 kHz for the yaw sensitive and 34kHz for the pitch sensitive probe. The steady aerodynamic characteristics of the probe were measured using the free jet probe calibration facility of the laboratory. The full set of calibration surfaces is given. Data acquisition is done with a fully automated traversing system, which moves the probe within the test rig and samples the signal with a PC-based A/D-board. An error analysis implemented into the data reduction routines revealed acceptable accuracy for flow angles as well as pressures for many turbomachinery flows. Depending on the dynamic head of the application the yaw angle is accurate within ±0.35° and pitch angle within ±0.7°. Finally, a comparison of time averaged results to five hole probe measurements is discussed.
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Ribeiro, Lucas, Juliana Oliveira, Dante Kuroiwa, Mohamed Kolko, Rodrigo Fernandes, Octaviano Junior, Nilva Moraes, Huber Vasconcelos, Talita Oliveira, and Mauricio Maia. "Advances in Vitreoretinal Surgery." Journal of Clinical Medicine 11, no. 21 (October 30, 2022): 6428. http://dx.doi.org/10.3390/jcm11216428.
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Advances in vitreoretinal surgery provide greater safety, efficacy, and reliability in the management of the several vitreoretinal diseases that benefit from surgical treatment. The advances are divided into the following topics: scleral buckling using chandelier illumination guided by non-contact visualization systems; sclerotomy/valved trocar diameters; posterior vitrectomy systems and ergonomic vitrectomy probes; chromovitrectomy; vitreous substitutes; intraoperative visualization systems including three-dimensional technology, systems for intraoperative optical coherence tomography, new instrumentation in vitreoretinal surgery, anti-VEGF injection before vitrectomy and in eyes with proliferative diabetic retinopathy, and new surgical techniques; endoscopic surgery; the management of subretinal hemorrhages; gene therapy; alternative techniques for refractory macular hole; perspectives for stem cell therapy and the prevention of proliferative vitreoretinopathy; and, finally, the Port Delivery System. The main objective of this review is to update the reader on the latest changes in vitreoretinal surgery and to provide an understanding of how each has impacted the improvement of surgical outcomes.
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Boletis, E., and C. H. Sieverding. "Experimental Study of the Three-Dimensional Flow Field in a Turbine Stator Preceded by a Full Stage." Journal of Turbomachinery 113, no. 1 (January 1, 1991): 1–9. http://dx.doi.org/10.1115/1.2927733.
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The paper describes the experimental investigation of the three-dimensional flow field through a low aspect ratio, high turning turbine stator preceded by a full stage. This configuration simulates as closely as possible the flow conditions for an intermediate stator in a multistage machine, although the use of cylindrical rotor blades does not reflect typical gas turbine design practice. The inlet conditions to the stator are significantly different from those reported in previous investigations dealing with tests in isolated cascades, e.g., Sieverding (1985); Marchal and Sieverding (1977); Sieverding et al. (1984); Klein (1969); Bindon (1979, 1980); Wegel (1970); and Boletis (1985). The inlet flow field to the stator is characterized by both radial and circumferential gradients. Inlet skew occurs on both endwalls but the overall shape does not resemble those that are generated in isolated cascades by rotating the upstream endwalls. Rotor clearance effects are of predominant importance for the flow field at the tip endwall region. The flow field is explored by means of double head four-hole pressure probes in five axial planes from upstream to far downstream of the stator. The results are presented in the form of contour plots and spanwise pitch-averaged distributions.
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Abdelfattah, S., and M. T. Schobeiri. "Experimental and numerical investigations of aerodynamic behavior of a three-stage high-pressure turbine at different operation conditions." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 226, no. 6 (October 26, 2011): 1535–49. http://dx.doi.org/10.1177/0954406211423725.
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Using the Reynolds-averaged Navier–Stokes-based numerical methods to simulate the flow field, efficiency and performance of high-pressure turbine components of multi-stage steam turbines result in substantial differences between the experimental and the numerical results pertaining to the individual flow quantities. These differences are integrally noticeable in terms of major discrepancies in aerodynamic losses, efficiency, and performance of the turbine. As a consequence, engine manufacturers are compelled to frequently calibrate their simulation package by performing a series of experiments before issuing efficiency and performance guaranty. The aim of this article is to investigate the cause of the aforementioned differences by utilizing a three-stage high-pressure research turbine with three-dimensional compound lean blades as the platform for experimental and numerical investigations. Experimental data were obtained using interstage aerodynamic measurements at three measurement stations, namely, downstream of the first rotor row, the second stator row, and the second rotor row. Detailed measurements were conducted using custom-designed five-hole probes traversed in both circumferential and radial directions. Aerodynamic measurements were carried out within a rotational speed range of 1800–2800 r/min. Numerical simulations were performed utilizing a commercially available computational fluid dynamics code. A detailed mesh of the three stages was created and used to simulate the corresponding operating conditions. The experimental and numerical results were compared following a critical discussion relative to differences mentioned above.
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Williams, John, Amer Samdani, Helton Luiz Aparecido Defino, Keri George, John Gaughan, and Randal Betz. "Anticipation of vertebral pedicle breach through dynamic surgical guidance." Coluna/Columna 13, no. 3 (September 2014): 210–13. http://dx.doi.org/10.1590/s1808-18512014130300r85.
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OBJECTIVE: To determine the effectiveness of a pedicle probe to anticipate an impending breach and allow redirection during placement of a pilot pedicle hole. METHODS: Purposely four cortical wall sites were drilled: medial and lateral pedicle wall, and lateral and anterior wall of the vertebral body. The surgeon stopped probing when the sound changed, suggesting abutment against the cortical wall ("anticipation" of impending breach). A fluoroscopy image was then obtained. The surgeon then advanced the PediGuard through the cortex until the sound changed, indicating a breach. In the second part of the study three probes were used: 1) DSG (PediGuard) with curved tip with electronics ON; 2) DSG with electronics OFF; 3) standard Lenke probe. After the images were taken, the operating surgeon (blinded to x-rays) was instructed to redirect and continue drilling into the vertebral body. RESULTS: The surgeon accurately anticipated 60 of 75 (80%) of the breaches, 17 of 19 (89%) in the medial pedicle wall. In the second part of the study the DSG with electronics ON was superior to the DSG with electronics OFF as well as the standard Lenke probe (100% vs. 90% vs. 79%, p = 0.0191). CONCLUSION: Successful redirection by passing the pedicle probes into the vertebral body without a breach after anticipation of an impending pedicle wall breach occurred in 100% of the drillings when done with the DSG with the electronics ON vs only 84% when there was no electronic feedback.
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Wang, Y., S. Komori, and Z. Xu. "Design and Performance Prediction of Centrifugal Impellers." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 210, no. 6 (December 1996): 463–76. http://dx.doi.org/10.1243/pime_proc_1996_210_073_02.
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This study presents a simple method for designing the blade geometry of a centrifugal compressor impeller. In this method, instead of giving the mean swirl distribution on the meridional surface, the blade angle distribution is specified and the blade shape is derived, making it easier to perform the design. The quasi-three-dimensional potential flow field inside the impeller is obtained using the streamline curvature method, which solves the Euler equation along arbitrary quasi-orthogonals. The viscous effect is incorporated indirectly into the inverse design of the impeller via the simplified three-dimensional boundary layer calculation and the performance prediction. A three-dimensional centrifugal impeller was designed using this inviscid-viscous method and eventually manufactured. The newly designed impeller (B) and another impeller (A) designed previously were tested on a standard apparatus for model impellers. With the aid of three-hole probes and thermocouples, the flow parameters downstream of the exit of the impellers were measured along the axial direction of the impellers. A viscous loss model related to the boundary parameters is developed and used for the performance predictions of the impellers together with other loss models. From both the boundary layer analysis and the performance prediction, it is concluded that impeller B is superior to impeller A, which is in close accordance with the measurements.
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Town, Jason, and Cengiz Camci. "A Time Efficient Adaptive Gridding Approach and Improved Calibrations in Five-Hole Probe Measurements." International Journal of Rotating Machinery 2015 (2015): 1–14. http://dx.doi.org/10.1155/2015/376967.
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Five-Hole Probes (FHP), being a dependable and accurate aerodynamic tool, are an excellent choice for measuring three-dimensional flow fields in turbomachinery. To improve spatial resolution, a subminiature FHP with a diameter of 1.68 mm is employed. High length to diameter ratio of the tubing and manual pitch and yaw calibration cause increased uncertainty. A new FHP calibrator is designed and built to reduce the uncertainty by precise, computer controlled movements and reduced calibration time. The calibrated FHP is then placed downstream of the nozzle guide vane (NGV) assembly of a low-speed, large-scale, axial flow turbine. The cold flow HP turbine stage contains 29 vanes and 36 blades. A fast and computer controllable traversing system is implemented using an adaptive grid method for the refinement of measurements in regions such as vane wake, secondary flows, and boundary layers. The current approach increases the possible number of measurement points in a two-hour period by 160%. Flow structures behind the NGV measurement plane are identified with high spatial resolution and reduced uncertainty. The automated pitch and yaw calibration and the adaptive grid approach introduced in this study are shown to be a highly effective way of measuring complex flow fields in the research turbine.
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Wilfert, G., and L. Fottner. "The Aerodynamic Mixing Effect of Discrete Cooling Jets With Mainstream Flow on a Highly Loaded Turbine Blade." Journal of Turbomachinery 118, no. 3 (July 1, 1996): 468–78. http://dx.doi.org/10.1115/1.2836692.
Full textAbstract:
For the application of film cooling to turbine blades, experimental investigations were performed on the mixing processes in the near-hole region with a row of holes on the suction suction side of a turbine cascade. Data were obtained using pneumatic probes, pressure tappings, and a three-dimensional subminiature hot-wire probe, as well as surface flow visualization techniques. It was found that at low blowing rates, a cooling jet behaves very much like a normal obstacle and the mixing mainly takes place in the boundary layer. With increasing blowing rates, the jet penetrates deeper into the mainstream. The variation of the turbulence level at the inlet of the turbine cascade and the Reynolds number showed a strong influence on the mixing behavior. The kidney-shaped vortex and as an important achievement the individual horseshoe vortex of each single jet were detected and their exact positions were obtained. This way it was found that the position of the horseshoe vortex is strongly dependent on the blowing rate and this influences the aerodynamic mixing mechanisms. A two-dimensional code for the calculation of boundary layer flows called GRAFTUS was used; however, the comparison with the measurements showed only limited agreement for cascade flow with blowing due to the strong three-dimensional flow pattern.
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Hsu, Yu-Te, Maarten Berben, Matija Čulo, Seiji Adachi, Takeshi Kondo, Tsuneshiro Takeuchi, Yue Wang, Steffen Wiedmann, Stephen M. Hayden, and Nigel E. Hussey. "Anomalous vortex liquid in charge-ordered cuprate superconductors." Proceedings of the National Academy of Sciences 118, no. 7 (February 12, 2021): e2016275118. http://dx.doi.org/10.1073/pnas.2016275118.
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The interplay between charge order and d-wave superconductivity in high-Tc cuprates remains an open question. While mounting evidence from spectroscopic probes indicates that charge order competes with superconductivity, to date little is known about the impact of charge order on charge transport in the mixed state, when vortices are present. Here we study the low-temperature electrical resistivity of three distinctly different cuprate families under intense magnetic fields, over a broad range of hole doping and current excitations. We find that the electronic transport in the doping regime where long-range charge order is known to be present is characterized by a nonohmic resistivity, the identifying feature of an anomalous vortex liquid. The field and temperature range in which this nonohmic behavior occurs indicates that the presence of long-range charge order is closely related to the emergence of this anomalous vortex liquid, near a vortex solid boundary that is defined by the excitation current in the T→ 0 limit. Our findings further suggest that this anomalous vortex liquid, a manifestation of fragile superconductivity with a suppressed critical current density, is ubiquitous in the high-field state of charge-ordered cuprates.
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Kronfeld, Klaus-Peter, Raminta Mazetyte-Stasinskiene, Xuejiao Zheng, and Johann Michael Köhler. "Textured and Hierarchically Constructed Polymer Micro- and Nanoparticles." Applied Sciences 11, no. 21 (November 5, 2021): 10421. http://dx.doi.org/10.3390/app112110421.
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Microfluidic techniques allow for the tailored construction of specific microparticles, which are becoming increasingly interesting and relevant. Here, using a microfluidic hole-plate-device and thermal-initiated free radical polymerization, submicrometer polymer particles with a highly textured surface were synthesized. Two types of monomers were applied: (1) methylmethacrylate (MMA) combined with crosslinkers and (2) divinylbenzene (DVB). Surface texture and morphology can be influenced by a series of parameters such as the monomer–crosslinker–solvent composition, surfactants, and additives. Generally, the most structured surfaces with the simultaneously most uniform particles were obtained in the DVB–toluene–nonionic-tensides system. In a second approach, poly-MMA (PMMA) particles were used to build aggregates with bigger polymer particles. For this purpose, tripropyleneglycolediacrylate (TPGDA) particles were synthesized in a microfluidic co-flow arrangement and polymerized by light- irradiation. Then, PMMA particles were assembled at their surface. In a third step, these composites were dispersed in an aqueous acrylamide–methylenebisacrylamide solution, which again was run through a co-flow-device and photopolymerized. As such, entities consisting of particles of three different size ranges—typically 0.7/30/600 µm—were obtained. The particles synthesized by both approaches are potentially suitable for loading with or incorporation of analytic probes or catalysts such as dyes or metals.
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Zhou, Huan, Zhengxiang Li, Zhiqi Huang, He Gao, and Lu Huang. "Constraints on the abundance of primordial black holes with different mass distributions from lensing of fast radio bursts." Monthly Notices of the Royal Astronomical Society 511, no. 1 (January 28, 2022): 1141–52. http://dx.doi.org/10.1093/mnras/stac139.
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ABSTRACT Primordial black holes (PBHs) has been considered to form a part of dark matter for a long time but the possibility has been poorly constrained over a wide mass range, including the stellar mass range ($1{-}100\ {\rm M}_{\odot }$). However, due to the discovery of merger events of black hole binaries by LIGO-Virgo gravitational wave observatories, the interest for PBHs in the stellar mass window has been aroused again. Fast radio bursts (FRBs) are bright radio transients with millisecond duration and very high all-sky occurrence rate. Lensing effect of these bursts has been proposed as one of the optimal probes for constraining the abundance of PBHs in the stellar mass range. In this paper, we first investigate constraints on the abundance of PBHs from the latest 593 FRB observations for both the monochromatic mass distribution and three other popular extended mass distributions related to different formation mechanisms of PBHs. It is found that constraints from currently public FRB observations are relatively weaker than those from existing gravitational wave detections. Furthermore, we forecast constraining power of future FRB observations on the abundance of PBHs with different mass distributions of PBHs and different redshift distributions of FRBs taken into account. Finally, We find that constraints of parameter space on extended mass distributions from ∼105 FRBs with $\overline{\Delta t}\le 1 ~\rm ms$ would be comparable with what can be constrained from gravitational wave events. It is foreseen that upcoming complementary multimessenger observations will yield considerable constraints on the possibilities of PBHs in this intriguing mass window.
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Rehder, Hans-Jürgen, and Axel Dannhauer. "Experimental Investigation of Turbine Leakage Flows on the Three-Dimensional Flow Field and Endwall Heat Transfer." Journal of Turbomachinery 129, no. 3 (July 20, 2006): 608–18. http://dx.doi.org/10.1115/1.2720484.
Full textAbstract:
Within a European research project, the tip endwall region of low pressure turbine guide vanes with leakage ejection was investigated at DLR in Göttingen. For this purpose a new cascade wind tunnel with three large profiles in the test section and a contoured endwall was designed and built, representing 50% height of a real low pressure turbine stator and simulating the casing flow field of shrouded vanes. The effect of tip leakage flow was simulated by blowing air through a small leakage gap in the endwall just upstream of the vane leading edges. Engine relevant turbulence intensities were adjusted by an active turbulence generator mounted in the test section inlet plane. The experiments were performed with tangential and perpendicular leakage ejection and varying leakage mass flow rates up to 2%. Aerodynamic and thermodynamic measurement techniques were employed. Pressure distribution measurements provided information about the endwall and vane surface pressure field and its variation with leakage flow. Additionally streamline patterns (local shear stress directions) on the walls were detected by oil flow visualization. Downstream traverses with five-hole pyramid type probes allow a survey of the secondary flow behavior in the cascade exit plane. The flow field in the near endwall area downstream of the leakage gap and around the vane leading edges was investigated using a 2D particle image velocimetry system. In order to determine endwall heat transfer distributions, the wall temperatures were measured by an infrared camera system, while heat fluxes at the surfaces were generated with electric operating heating foils. It turned out from the experiments that distinct changes in the secondary flow behavior and endwall heat transfer occur mainly when the leakage mass flow rate is increased from 1% to 2%. Leakage ejection perpendicular to the main flow direction amplifies the secondary flow, in particular the horseshoe vortex, whereas tangential leakage ejection causes a significant reduction of this vortex system. For high leakage mass flow rates the boundary layer flow at the endwall is strongly affected and seems to be highly turbulent, resulting in entirely different heat transfer distributions.
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Abuter, R., N. Aimar, A. Amorim, J. Ball, M. Bauböck, J. P. Berger, H. Bonnet, et al. "Mass distribution in the Galactic Center based on interferometric astrometry of multiple stellar orbits." Astronomy & Astrophysics 657 (January 2022): L12. http://dx.doi.org/10.1051/0004-6361/202142465.
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Stars orbiting the compact radio source Sgr A* in the Galactic Center serve as precision probes of the gravitational field around the closest massive black hole. In addition to adaptive optics-assisted astrometry (with NACO/VLT) and spectroscopy (with SINFONI/VLT, NIRC2/Keck and GNIRS/Gemini) over three decades, we have obtained 30–100 μas astrometry since 2017 with the four-telescope interferometric beam combiner GRAVITY/VLTI, capable of reaching a sensitivity of mK = 20 when combining data from one night. We present the simultaneous detection of several stars within the diffraction limit of a single telescope, illustrating the power of interferometry in the field. The new data for the stars S2, S29, S38, and S55 yield significant accelerations between March and July 2021, as these stars pass the pericenters of their orbits between 2018 and 2023. This allows for a high-precision determination of the gravitational potential around Sgr A*. Our data are in excellent agreement with general relativity orbits around a single central point mass, M• = 4.30 × 106 M⊙, with a precision of about ±0.25%. We improve the significance of our detection of the Schwarzschild precession in the S2 orbit to 7σ. Assuming plausible density profiles, the extended mass component inside the S2 apocenter (≈0.23″ or 2.4 × 104 RS) must be ≲3000 M⊙ (1σ), or ≲0.1% of M•. Adding the enclosed mass determinations from 13 stars orbiting Sgr A* at larger radii, the innermost radius at which the excess mass beyond Sgr A* is tentatively seen is r ≈ 2.5″ ≥ 10× the apocenter of S2. This is in full harmony with the stellar mass distribution (including stellar-mass black holes) obtained from the spatially resolved luminosity function.
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Pfau, A., J. Schlienger, D. Rusch, A. I. Kalfas, and R. S. Abhari. "Unsteady Flow Interactions Within the Inlet Cavity of a Turbine Rotor Tip Labyrinth Seal." Journal of Turbomachinery 127, no. 4 (March 1, 2003): 679–88. http://dx.doi.org/10.1115/1.2008973.
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This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth seal of a two stage axial research turbine. Highly resolved, steady and unsteady three-dimensional flow data are presented. The probes used here are a miniature five-hole probe of 0.9 mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth seal configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focusing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.
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Shi-Zhong, Zhang, Xu Ru-Xiang, Zhou Yuan, Zhang Ji-Ren, Liu Zhi-Liang, Zhang Wang-Ming, and Wang Sen-Ming. "Targeted Cryosurgery for the Treatment of Cerebral Glioma with Cryocare Surgical System Guided by Stereotactic Technology." Technology in Cancer Research & Treatment 6, no. 5 (October 2007): 153303460700600. http://dx.doi.org/10.1177/1533034607006005012.
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This study is to investigate the therapeutic effects of cryoablation guided by stereotactic technology for targeted cryosurgery of patients with cerebral glioma. The Cosman-Roberts-Wells (CRW) stereotactic apparatus and brain CT (Computed tomography) scan were applied to define the coordinates of the center and marginal points of the glioma. Twelve cases with recurrent glioma were treated by freezing-re-warming-freezing therapy in designated targets with cryocare surgical system's therapeutic probes. One patient, whose temporal tumor was 3.5cm in diameter, underwent drilling-hole cryoablation without resection in the central target of the tumor; the other eleven patients, whose maximum diameters of frontal and occipitoparietal tumors were between 4.5–9cm, underwent stereotactic volumetric resection and the frozen tumor tissues were removed after intraoperative freezing. Postoperative CT scans indicated that glioma tissues and regions 1cm surrounding the tumors in the eleven cases were excised, and no postoperative hemorrhage or remarkable edema was noted; staining of lesions in the case undergoing direct cryosurgery vanished in reexamination two weeks after the treatment, CT density declined and lesions had a tendency to become malacic. One case whose hemiparesis aggravated after operation recovered after symptomatic treatment and one case with poor prognostic scalp incision recovered after scalp flap transposition. The average follow-up duration was 2.6 years in the eleven cases. Eight cases with astrocytic glioma survived, among which three cases recurred and five did not. One case with astrocytic glioma died 1.5 years later and one died 2 years later. The patient with glioblastoma died after 1.2 years. Stereotaxy-guided cryoablation of cerebral glioma can remove brain tumor totally, less traumatic and less hemorrhagic than conventional approaches, it is safe and convenient to perform. Therefore, it may have an encouraging future in clinical applications, though its long-term efficacies still await further observation due to defects in its manipulation.
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Toso, Raffaella, Hua Zhu, and Rodney M. Camire. "Alteration of the Factor X Zymogen to Protease Transition Provides Evidence for Allosteric Linkage between the S1 and FVa Binding Sites." Blood 106, no. 11 (November 16, 2005): 30. http://dx.doi.org/10.1182/blood.v106.11.30.30.
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Abstract The zymogen to protease transition in the chymotrypsin-like serine protease family follows a well described mechanism in which bond cleavage at a highly conserved site (Arg15-Ile16; chymotrypsin numbering system) results in the unmasking of a new N-terminus that acts as an intramolecular ligand for Asp194. This new salt-bridge drives a conformational change in the so-called “activation domain”, surface loops consisting of the S1 specificity pocket, oxyanion hole, autolysis loop, and sodium biding site. It is well documented in the trypsin system that Ile16-Asp194 internal salt-bridge formation is allosterically linked to the S1 specificity site; that is changes at one site influence the other and vice versa. Blood coagulation factor Xa (FXa) reversibly associates with its cofactor factor Va (FVa) on a membrane surface in the presence of Ca2+ ions with high affinity; an interaction which is not mimicked by the zymogen FX. To determine whether the FX zymogen to protease transition contributes to the expression of a high affinity FVa binding site, we constructed a series of FXa variants which are shifted along this transition pathway. To generate these “zymogen-like” proteins, we made several substitutions at position 16 or 17, with the intent of destabilizing the intramolecular salt bridge to varying degrees. Following a series of preliminary experiments, three mutants were chosen for expression, purification, and activation with RVV-X: I16L, I16G, and V17A. Kinetic studies using peptidyl substrates and active site directed probes revealed that I16L and V17A have an impaired ability to bind these probes (15 to 25-fold increase in the Km or Ki) while the rate of catalysis (kcat) was reduced by 3-fold compared to wild-type FXa (wtFXa; plasma-derived and recombinant). The I16G variant was not inhibited by any of the probes examined and its chromogenic activity was severely impaired (>500 to 1000-fold), precluding calculation of kinetic parameters. These data are consistent with the idea that destabilization of internal salt-bridge formation (Ile16-Asp194) influences binding at the S1 specificity site. In contrast to these results, assembly of I16L and V17A into prothrombinase almost completely restored the Km for peptidyl substrates while the kcat was still 3-fold reduced, indicating that FVa binding can rescue binding at the active site. Surprisingly, even the Km value for I16G was almost completely restored (3-fold increased compared to wtFXa) when assembled in prothrombinase; however a 60-fold reduction in the kcat was found. Consistent with these data, kinetic studies using prothrombin or prethrombin-1 revealed that each of the FXa variants had a normal Km value when assembled in prothrombinase; while the kcat values where reduced to a similar extent as for the chromogenic substrates. Overall our data indicate that direct binding of these FXa variants to FVa rescues binding at S1 site, suggesting allosteric linkage exists between these sites. Thus the FX zymogen to protease transition not only influences the formation of the S1 pocket, but also contributes in a substantial way to the formation of a FVa binding site.
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Nguyen, Thi Hoang Thao, Sungwon Park, Dongmin Jang, and Jungkyu Ahn. "Evaluation of Three-Dimensional Environmental Hydraulic Modeling in Scour Hole." Applied Sciences 12, no. 8 (April 15, 2022): 4032. http://dx.doi.org/10.3390/app12084032.
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The main goal of this study was comparing the performance of an open-source code OpenFOAM and a commercial software Ansys Fluent in simulating the turbulent flow through a scour hole developed in a sand bed channel, which helps to give a hint in choosing the appropriate calculating tool. Both models were set with the same mesh and as similar as possible numerical settings, with RANS turbulence modeling, applying the k-ωSST model, in transient simulations. The results of flow pattern, velocity, and turbulence properties were collected and compared with laboratory experimental data. The analyzed results showed that, although both of the two models cannot perfectly reproduce the values from a laboratory experiment, they can quite well capture the flow in scour hole near the wall, with a bit higher performance coming from the OpenFOAM model application.
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Braun, Michaela, Haley Wecker, Kara Dunmire, Caitlin Evans, Michael W. Sodak, Maks Kapetanovich, Jerry Shepherd, et al. "Evaluation of Hammermill Tip Speed, Air Assist, and Screen Hole Diameter on Ground Corn Characteristics." Processes 9, no. 10 (October 1, 2021): 1768. http://dx.doi.org/10.3390/pr9101768.
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This study was performed to evaluate hammermill tip speed, assistive airflow, and screen hole diameter on hammermill throughput and characteristics of ground corn. Corn was ground using two Andritz hammermills measuring 1 m in diameter each equipped with 72 hammers and 300 HP motors. Treatments were arranged in a 3 × 3 × 3 factorial design with three tip speeds (3774, 4975, and 6176 m/min), three screen hole diameters (2.3, 3.9, and 6.3 mm), and three air flow rates (1062, 1416, and 1770 fan revolutions per minute). Corn was ground on three separate days to create three replications and treatments were randomized within day. Samples were collected and analyzed for moisture, particle size, and flowability characteristics. There was a 3-way interaction (p = 0.029) for standard deviation (Sgw). There was a screen hole diameter × hammer tip speed interaction (p < 0.001) for geometric mean particle size dgw (p < 0.001) and composite flow index (CFI) (p < 0.001). When tip speed increased from 3774 to 6176 m/min, the rate of decrease in dgw was greater as screen hole diameter increased from 2.3 to 6.3 mm. For CFI, increasing tip speed decreased the CFI of ground corn when ground using the 3.9 and 6.3 mm screen. However, when grinding corn using the 2.3 mm screen, there was no evidence of difference in CFI when increasing tip speed. In conclusion, the air flow rate did not influence dgw of corn, but hammer tip speed and screen size were altered and achieved a range of dgw from 304 to 617 µm.
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Wu, Yuling, Weixuan Zhang, Fang Qian, Haocheng Zhao, Kunpeng Guo, Mixue Wang, Xuefeng Li, Zhike Liu, Hua Wang, and Bingshe Xu. "An efficient phenylaminecarbazole-based three-dimensional hole-transporting materials for high-stability perovskite solar cells." Dyes and Pigments 182 (November 2020): 108663. http://dx.doi.org/10.1016/j.dyepig.2020.108663.
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Righi, Giulia, Julius Plescher, Franz-Philipp Schmidt, R. Kramer Campen, Stefano Fabris, Axel Knop-Gericke, Robert Schlögl, Travis E. Jones, Detre Teschner, and Simone Piccinin. "On the origin of multihole oxygen evolution in haematite photoanodes." Nature Catalysis 5, no. 10 (October 19, 2022): 888–99. http://dx.doi.org/10.1038/s41929-022-00845-9.
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AbstractThe oxygen evolution reaction (OER) plays a crucial role in (photo)electrochemical devices that use renewable energy to produce synthetic fuels. Recent measurements on semiconducting oxides have found a power law dependence of the OER rate on surface hole density, suggesting a multihole mechanism. In this study, using transient photocurrent measurements, density functional theory simulations and microkinetic modelling, we have uncovered the origin of this behaviour in haematite. We show here that the OER rate has a third-order dependence on the surface hole density. We propose a mechanism wherein the reaction proceeds by accumulating oxidizing equivalents through a sequence of one-electron oxidations of surface hydroxy groups. The key O–O bond formation step occurs by the dissociative chemisorption of a hydroxide ion involving three oxyl sites. At variance with the case of metallic oxides, the activation energy of this step is weakly dependent on the surface hole coverage, leading to the observed power law.
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Alshoaibi, Abdulnaser M. "Numerical Modeling of Crack Growth under Mixed-Mode Loading." Applied Sciences 11, no. 7 (March 26, 2021): 2975. http://dx.doi.org/10.3390/app11072975.
Full textAbstract:
The aim of this paper is to simulate the propagation of linear elastic crack in 3D structures using the latest innovation developed using Ansys software, which is the Separating Morphing and Adaptive Remeshing Technology (SMART), in order to enable automatic remeshing during a simulation of fracture behaviors. The ANSYS Mechanical APDL 19.2 (Ansys, Inc., Canonsburg, PA, USA), is used by employing a special mechanism in ANSYS, which is the smart crack growth method, to accurately predict the crack propagation paths and associated stress intensity factors. For accurate prediction of the mixed-mode stress intensity factors (SIFs), the interaction integral technique has been employed. This approach is used for the prediction of the mixed-mode SIFs in the three-point bending beam, which has six different configurations: three configurations with holes, and the other three without holes involving the linear elastic fracture mechanics (LEFM) assumption. The results indicated that the growth of the crack was attracted to the hole and changes its trajectory to reach the hole or floats by the hole and grows when the hole is missing. For verification, the data available in the open literature on experimental crack path trajectories and stress intensity factors were compared with computational study results, and very good agreement was found.
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Martinkovič, Maroš, Peter Pokorný, and Petra Bodišová. "Influence of Drill Wear to Local Plastic Deformation in the Wall of Drilling Hole." Key Engineering Materials 606 (March 2014): 77–80. http://dx.doi.org/10.4028/www.scientific.net/kem.606.77.
Full textAbstract:
Final properties of plastic deformed parts of workpieces are affected by production technological processes. Therefore it is needful to know detailed structure changes of plastic deformed material caused by machining - grinding, drilling etc. Friction of tool to work surface caused one of three areas of plastic deformation in cutting zone. It has great influence to quality of work surface and local mechanical properties of surface layer of workpiece. Influence of drill wear to local plastic deformation in deformation zone around the surface of drilled holes was investigated. Two types of cutting tools were used: high speed steel drill IZAR HSSCO with diameter 6,0 mm surface hardened by boriding and the same one without boride layer. Standard cutting parameters were used. During the machining process, axial component of cutting force and torque were observed. The work piece was bulk from carbon steel Ck45 (1.0503). Wear of the tool was estimated as a wide of wear on tool flank. The local strain in analysed place of probes on their sections was obtained by stereological measurement of degree of grain boundaries orientation, which is proportional to grain boundaries deformation degree. Estimation of grain boundary orientation degree leads to determination of local plastic deformation in arbitrary place of workpiece. These results lead to detailed analysis of material structure changes caused by drilling from which local mechanical properties result.
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Xie, Chenshuo, Jianming Kang, Qiangji Peng, Xiaoyu Wang, Yingkai Chen, Chunyan Zhang, and Ningning Zhang. "Optimization of Screen-Hole-Clearing Devices for Mechanized Residual Film–Impurity Separation." Applied Sciences 12, no. 22 (November 16, 2022): 11658. http://dx.doi.org/10.3390/app122211658.
Full textAbstract:
The airflow velocity in some nozzles is low, and the clearing of the nozzle is ineffective because of unreasonable airflow pipe arrangements and the distance from the nozzle to the screen surface of screen-hole-clearing devices for trommel-sieve-type residual film–impurity wind separators. In the present study, the main structure and working parameters affecting the screen hole clogging situation were determined through theoretical analysis and computational fluid dynamics simulations. In addition, a three-factor, three-level quadratic regression orthogonal center of rotation combination test was performed. The distance from the nozzle to the screen surface, fan wind speed, and the number of airflow pipes were selected as test factors, and the ratio of impurities in the residual film and the blockage ratio of the screen holes were selected as the evaluation indexes. The results indicated that the ratio of impurities in the residual film was reduced by 2.42% and the blockage ratio of the screen holes was reduced by 1.92% at a nozzle-to-screen distance of 102 mm, a fan wind speed of 24 m/s, and with four air pipes. The resulting impurity ratio in the film was 5.86%, and the blockage ratio of screen pores was 5.41%. The minimum airflow velocity of 15.8 m/s at each nozzle position of the optimized screen-hole-clearing device satisfied the requirements of screen hole clearing and blockage. Furthermore, the ratio of impurities in the residual film and the blockage ratio of the screen holes remained unchanged during the continuous operation of the device. This indicated that the optimized screen-hole-clearing device had a stable working performance. This study may provide a theoretical framework for the future development of screen-hole--clearing devices.