Prismatic Blades Research Articles

Experimental investigation of an entropy production in a linear blade cascade

The vortical structures in turbomachinery are crucial phenomena that significantly impact the machine’s efficiency. Therefore, investigating them is essential for a better understanding of the machine’s operation.The presented paper focuses on an experimental investigation of entropy production in a linear blade cascade composed of prismatic blades for two pitch-to-chord ratios, t/c = 0.6, and 0.9. The effects of the inlet flow angle, α1 = −20°, 5°, 30°, and outlet isentropic Reynolds number, Re2,is = (0.8, 1.2, 2.5, and 4.5) × 105, are examined based on pressure measurements.Entropy production is evaluated as a balance of fluxes through the inlet and outlet boundaries of the control volume. The paper provides a detailed discussion of the local distribution of entropy production and vorticity in the flow field, as well as their evolution with the tested parameters. The correlations between the integral values of entropy production and the tested parameters are also given.

Shock wave configuration in a transonic flow through a mid-section of a last stage turbine blade cascade equipped with a part-span connector

This paper deals with the study of a flow field and namely the configuration of shock waves in a blade cascade equipped with a part-span connector called tie-boss. The cascade consists of prismatic blades formed from the mid-section of a very long last-stage blade of a steam turbine. The study is based on numerical simulations of the flow through a cascade that was previously tested in a wind tunnel. Commercial software Ansys CFX was used for the simulations and Ansys ICEM for the mesh generation. The computational domain contains non-homogenous mesh interfaces. The simulations showed that the presence of the tie-boss has a profound effect on the configuration of the shock waves. The blade exit shock waves are disturbed and new lateral shock waves are introduced into the flow.

The Proceduralization of Hominin Knapping Skill: Memorizing Different Lithic Technologies

Reconstructing the technical and cognitive abilities of past hominins requires an understanding of how skills like stone toolmaking were learned and transmitted. We ask how much of the variability in the uptake of knapping skill is due to the characteristics of the knapping sequences themselves? Fundamental to skill acquisition is proceduralization, the process whereby skilful tasks are converted from declarative memories (consciously memorized facts and events) into procedural memories (sub-consciously memorized actions) via repetitive practice. From knapping footage, we time and encode each action involved in discoidal, handaxe, Levallois and prismatic blade production. The structure and complexity of these reduction sequences were quantified using k-mer analysis and Markov chains. The amount of time spent on tasks and the pattern of core rotations revealed portions of these reduction sequences that are predisposed to being converted into procedural memories. We observed two major pathways to achieve this proceduralization: either a repetitive or a predictable sequence of core rotations. Later Acheulean handaxes and Levallois knapping involved a predictable platform selection sequence, while prismatic blade knapping involved a repetitive exploitation of platforms. Technologies and the portions of their reduction sequence that lend themselves to proceduralization probably facilitated the more rapid uptake of stone toolmaking skill.

Teotihuacan site 19:N1W5: Mortuary and oxygen isotope evidence for a Michoacan affiliation

AbstractSite E19 (19:N1W5), near Tlailotlacan, the “Zapotec Barrio” of Teotihuacan, contains evidence of both Tlailotlacan and Michoacan affiliation. To verify and better understand the Michoacan relationship, 22 enamel and 19 bone samples from five E19-affiliated burials were analyzed to determine their oxygen isotope compositions, which provide an indication of an individual's area of residence when that particular tissue was forming. Because prismatic blades and Thin Orange ceramics from Teotihuacan occur widely in the Lakes Region of north central Michoacan we obtained samples from several sites there for comparative purposes. The results show that most of the E19 people had passed their later years in the Patzcuaro Basin of the Lakes Region. Although in E19 the archaeological evidence of this relationship declined over time, the isotopic evidence indicates that Patzcuaro ties continued to the end of E19's occupation. It seems that the people of E19, originally Michoacanos, gradually adopted a core identity as Teotihuacanos while continuing to deploy their Michoacan ancestry during their stays in Michoacan.

New Concept for Design in Turbomachinery Applications Using Full RANS Gradient Methodology

Abstract Centrifugal compressors are mainly designed with the best efficiency point in mind and the focus oriented toward the impeller. The vaned diffuser geometry is usually developed using simple shapes, such as prismatic blades or wedges, which are unable to account for the flow distortion at the impeller outlet. Investigations of diffuser modifications using computational fluid dynamics (CFD) during the design phase can help to extend the operating range. In order to assess the effect of such modifications, simulations in off-design conditions need to be performed. Accurate predictions of local flow structures at such conditions require a robust flow solver with mixing-plane interfaces and advanced turbulence modeling capabilities. In recent years diffuser modifications were performed mainly based on manual trial-and-error approaches and show considerable potential for improvements. To accelerate the process and allow automation, which is crucial in industrial applications, it is suggested to use an adjoint-based optimization algorithm for diffuser shape design. In this work, a discrete adjoint solver implemented into a robust pressure-based CFD framework was used. While many optimization studies follow the frozen-turbulence approach, which essentially ignores the dependency of the sensitivity on the turbulence quantities, the present adjoint solver fully includes such effects. Automatic differentiation even allows for flexibility with respect to the choice of turbulence model. Any model available in the primal solver can also be used in the adjoint solver. In this particular case, the k–ɛ enhanced wall treatment model was used, since it shows good convergence behavior and is capable of predicting the machine characteristic even at off-design conditions. Mesh morphing was realized via the free-form deformation method, which provides stable mesh deformation and offers a simple and fast setup procedure. Several optimizations were conducted for the RWTH Aachen “Radiver” centrifugal compressor case with vaned diffuser. It was shown that an optimization strategy using a multi-operating point approach, considering part- and overload conditions, is capable of improving the peak efficiency as well as the overall shape of the machine characteristic.

Filling in the Blanks: Standardization of Lithic Flake Production Throughout the Stone Age

ABSTRACT Standardization can be applied to a lithic assemblage via raw material selection, blank production, blank selection, and/or retouch. Here we explore the baseline level of morphological standardization achievable through blank production alone. By quantifying how little morphological variability is inherently involved in different blank-producing lithic technologies that span much of the Stone Age, we seek to gain a long-term perspective on the evolution of lithic standardization. 728 flakes were knapped from 26 cores of 7 different lithic technologies: bipolar, multiplatform, discoidal, Levallois, direct percussion prismatic blade, indirect percussion prismatic blade, and pressure prismatic blade. Using generalized Procrustes analyses of blank outlines, we observed three noticeable jumps in shape standardization: between bipolar and free-hand flaking, between flake and blade technologies, and between the percussive blade and pressure blade technologies. Technologies that involve more skill and more investment in core preparation appear to create a more standardized set of blanks.

Macanas in the Postclassic Maya Lowlands? A Preliminary Look

ABSTRACT Abundant obsidian prismatic blade segments in late (Late Postclassic/Colonial; ca. AD 1300–1700) lowland Maya lithic assemblages, generally ignored, are evaluated against the possibility that they were used in macanas, broadsword-like weapons resembling the Aztec macuahuitl, as attested by Spanish chroniclers. Measurements of 4,664 segments, proximal, medial, and distal, from seven sites around the central Peten (Guatemala) lakes, plus Tipu and Santa Rita Corozal (Belize) and Mayapan (Yucatan, Mexico), were analyzed. Segment dimensions are highly variable, both within and between sites, but appear to have had two modal sizes, rectangular (minimally 12 × 8 mm) and smaller and squarish (around 10–12 mm square). Macanas themselves also may have been made in two sizes, small and large. Although it cannot be proven that the segments were used in Maya macanas, the possibility warrants further study.

Stone toolmaking difficulty and the evolution of hominin technological skills

Stone tools are a manifestation of the complex cognitive and dexterous skills of our hominin ancestors. As such, much research has been devoted to understanding the skill requirements of individual lithic technologies. Yet, comparing skill across different technologies, and thus across the vast timespan of the Palaeolithic, is an elusive goal. We seek to quantify a series of commensurable metrics of knapping skill across four different lithic technologies (discoids, handaxes, Levallois, and prismatic blades). To compare the requisite dexterity, coordination, and care involved in each technology, we analysed video footage and lithic material from a series of replicative knapping experiments to quantify deliberation (strike time), precision (platform area), intricacy (flake size relative to core size), and success (relative blank length). According to these four metrics, discoidal knapping appears to be easiest among the sample. Levallois knapping involved an intricate reduction sequence, but did not require as much motor control as handaxes and especially prismatic blades. Compared with the other Palaeolithic technologies, we conclude that prismatic blade knapping is set apart by being a skill intensive means of producing numerous standardised elongate end-products.

Prismatic Blade Production at the Sinclair Site, Tennessee: Implications for Understanding Clovis Technological Organization

The Tennessee Division of Archaeology documented an extensive Paleoindian lithic quarry and workshop at the Sinclair site in Tennessee in 2008. We present the first detailed description of the lithic assemblage here, which focuses on aspects of its prismatic blade technology. Quantitative and qualitative attributes of 117 blades are assessed to characterize the assemblage and investigate human behaviors related to its formation. We then compare the blades from Sinclair to other blade assemblages. Blades at Clovis workshop sites are large and generally unstandardized. Mobile Clovis bands selected long, highly standardized blades from workshop sites, cached them as resource insurance, and crafted and used them as tools at campsites. The prismatic blade assemblage at Sinclair and other sites throughout the Midsouth suggests that this region played an important role in the development of prismatic blade technology at the end of the Pleistocene.

Numerical modelling and experimental investigation of the influence of selected geometric elements on the working characteristics of radial compressor stages with prismatic blades

The article deals with a description of basic results of research of radial compressor stages with 2D e.g. prismatic rotor blades. The experimental facility and the measurement and evaluation process are described briefly in the first part. The second part of this contribution is the numerical simulation and evaluation of the influence of the technological holes in the 2D rotor blades to compressor stage characteristics. The influence of the labyrinth seals clearance on the working characteristics can be found in the last part. The comparison of measured and computed values is presented and discussed.

Pachuca Obsidian Blades from the U.S. Southwest: Implications for Mesoamerican Connections and Coronado's Mexican Indian Allies

The connection between people in the prehispanic U.S. Southwest / Northwest Mexico (SW/NW) and Mesoamerica is one of the most debated research topics in American archaeology. SW/NW groups used objects from Mesoamerica, but did they also trade for obsidian? Archaeologists have yet to find Mesoamerican obsidian from confirmed prehispanic SW/NW contexts, but here we discuss four green obsidian prismatic blades from New Mexico and Arizona. Using EDXRF spectrometry, we demonstrate that the blades are from the Pachuca source in Mesoamerica. The blades were found at four sites that the Spanish and their Mexican Indian allies used or potentially visited beginning in AD 1540. Using lithic technological organization and historical narratives, we assess the credibility of the different hypothesized models of prehispanic SW/NW-Mesoamerican interaction and obsidian use by the Mexican Indian allies. We suggest that green Pachuca blades would have been traded into the SW/NW if interaction with Mesoamerica had occurred more frequently. We also offer reasons why archaeologists have found so few Mesoamerican obsidian blades at post-1540 sites. This research is relevant because it expands our knowledge about SW/NW-Mesoamerican connections and the Mexican Indian allies of the Spanish, who are an underrepresented group in the archaeological and historical records.

Outlining the knapping techniques: Assessment of the shape and regularity of prismatic blades using elliptic Fourier analysis

An important aspect of prismatic blade production is the choice of a knapping technique. This study tests the utility of elliptic Fourier analysis (EFA) for discriminating between different knapping techniques and offers a new perspective on blade variability. Our results indicate that there is an overlap in the outline shape and symmetry of individual blades produced by direct percussion, indirect percussion, and pressure debitage. Nevertheless, the EFA points out certain group-level differences regarding the shape and regularity of blade outlines and yields classification accuracy which is comparable to the previously proposed quantitative approaches for distinguishing blades produced by different knapping techniques. However, a more detailed analysis of technique-related factors shows that the emerging variability of blade outlines is more complex and that tripartite division might not always be suitable for reconstructing the past knapping behavior. We discuss the advantages and disadvantages of this method, and how it could complement the standard technological analysis in exploring and explaining blade variability.

Core and Periphery: Obsidian Craft Production in Late Postclassic (a.d. 1250/1300–1519) Tlaxcallan, Mexico

ABSTRACT This work present results of an analysis of supply, use, and production of obsidian artifacts in Tepeticpac and Metepec, two settlements of Late Postclassic (a.d. 1250/1300–1519) Tlaxcallan. The first sample (n = 9222) was recovered in two architectural compounds at Tepeticpac, a first-order settlement and part of the Tlaxcallan urban core. Tepeticpac materials exhibit a strong focus on prismatic blade production intended mainly for ceremonial or ritual use. The second sample (n = 14,915) comes from an architectural compound and a nearby obsidian discard area in Metepec, a peripheral second-order site. Metepec artifacts focused on the production of blades and bifacials, with greater evidence of different phases of obsidian processing indicating the presence of a nearby obsidian workshop. Comparison of obsidian craft production from both sites points towards decentralized craft production at Tlaxcallan and an open market economy for obsidian acquisition and consumption but also to marked political and socioeconomic hierarchies within the polity.

Obsidian exchange networks in the Jovel Valley, Chiapas, Mexico: A compositional analysis approach

This article presents an analysis of obsidian artifacts from Maya archaeological sites in the Jovel Valley of highland Chiapas. The sites were all occupied during the Late Classic (AD 600–900) and Early Postclassic (AD 900–1250) periods, and include Moxviquil and CV-38, two small monumental centers on opposite sides of the valley, and Huitepec, a residential site on the southwest edge of the valley. 165 artifacts excavated by the Proyecto Económico de los Altos de Chiapas in 2009 and 2015 (164 obsidian artifacts and 1 glass) were analyzed using x-ray fluorescence spectrometry and the results were compared to known volcanic sources in Mesoamerica. The results indicate a significant bifurcation of dominant sources between sites on both sites of the valley, which, we conclude, also had a temporal aspect. Artifacts from CV-38 were predominantly from the San Martín Jilotepeque source, and were primarily associated with Late Classic period occupation, while artifacts from outlying areas at Moxviquil and Huitepec were predominantly from the El Chayal source and a small number of Central Mexican sources, and were primarily associated with Early Postclassic period occupation. Most artifacts in the study sample were 3rd series prismatic blade sections, originating from multiple obsidian sources. A unique notched prismatic blade eccentric recovered at Moxviquil likely represents an effigy stingray spine, and was likely a ceremonial object used by the site’s residents.

A REGIONAL ASSESSMENT OF OBSIDIAN USE IN THE POSTCLASSIC AZTATLAN TRADITION

AbstractOf the many items that were traded throughout the Postclassic (A.D. 850/900–1350) Aztatlan network, obsidian was perhaps the most prevalent. In this study, large assemblages of obsidian from five Aztatlan centers on the coastal plain are discussed: San Felipe Aztatan, Chacalilla, Amapa, Coamiles, and Peñitas. In total, over 12,000 obsidian artifacts were analyzed macroscopically and through handheld portable X-ray fluorescence. The results of these analyses illustrate regional patterns of obsidian use that appear consistent across the coastal plain. Generally, only three obsidian sources were used with frequency. The most proximal source was utilized for generalized reduction and probably acquired directly, while more distant obsidians from the Jalisco highlands are commonly found in the form of prismatic blades. These trends in obsidian use indicate an increase in source diversity concurrent with the development of the Aztatlan trade networks despite the local availability of quality obsidians. Finally, synchronic patterns of source distribution further indicate that sources were unevenly distributed as certain individuals likely had greater access to imported blades. In conclusion, this large study provides a regional perspective of obsidian use in Western Mexico on the coastal plain and showcases the pervasiveness of the obsidian trade during the Postclassic.

Novopetrovka III—an Early Neolithic Site in the Western Amur Basin and Its Chronology

This article discusses the chronology of Novopetrovka III—a Neolithic settlement in the Western Amur basin, evaluated by the radiocarbon analysis of charred remains on pottery. The Novopetrovka culture as a whole, represented by Novopetrovka I-III and Konstantinovka sites, which had been excavated in the early 1960s, was dated to the 5th (possibly 6th) to early 4th millennia BC on the basis of the typology of the blade industry. The overview of data on prismatic blades manufactured by the pressure technique demonstrated that blade industries appeared in a vast territory of Eurasia in the Final Pleistocene to Early Holocene and, in certain regions, survived until the Chalcolithic. Therefore, they are only a rough guide to the relative chronology of the sites. In the 1990s, after the appearance of radiocarbon dates generated from samples of organic remains in temper and charred remains on pottery from Novopetrovka II, the culture was redated to 15.5-10.8 cal BP. A comparative analysis of new radiocarbon dates based on charred remains on pottery suggests that the age of Novopetrovka III is 9.0-9.5 thousand years. Because no changes were traced in the Novopetrovka sites over a long period of time, the chronological assessment of the Novopetrovka culture in toto and of its separate sites is problematic.

Obsidian on the Periphery: Importation, Production, and Raw Material Husbandry in Oaxaca

ABSTRACT This study uses data collected during three seasons of survey and excavation to examine evidence for the importation of obsidian and the production of tools, particularly blades, in the periphery of obsidian exchange spheres in the Nejapa/Tavela region of Oaxaca, Mexico. Sourcing information from X-Ray Fluorescence reveals a wide-ranging and shifting utilization of both Mexican and Guatemalan sources. Differences in the assemblages from contemporaneous sites hint at the social and political complexity of the region, which was inhabited by Zapotec, Mixe, and Chontal language speakers in multiethnic communities. Visible manufacturing errors and evidence of recovery techniques suggest that local artisans were capable producers of prismatic blades, demonstrating invaluable skills in a region where obsidian was scarce. The paucity of raw material and artisan skill is attested by relatively low frequencies of obsidian, as well as by deliberate manufacturing techniques designed to maximize the output of blades from each core.

Design of an Axial Turbine for Highly Downsized Internal Combustion Engines

This paper describes and discusses the development of an axial turbocharger turbine concept as a potential substitute to commercial radial turbines for high-volume production. As turbo-lag is one of the main issues related to the inertia of the rotating parts in a turbocharger, leading to less responsive and drive-cycle efficient power units, the use of axial turbines, with their inherently lower inertia than radial types for the same application, enables the efficient reduction of the spool-up time of the system, to the benefit of the driving experience and emissions. However, axial turbines for this application usually show complicated blades and level of twist, leading to efficient but expensive designs compared to their radial counterparts. Based on this challenge, the idea of comparing prismatic (generally less efficient, but cheaper) and twisted 3D-bladed axial turbines showed that for lower blade aspect ratios, the efficiency is of the same order. For these reasons, many turbines with a range of different sizes were designed with both layouts (3D and prismatic blades) and compared. Further, the use of 3D optical scanning, as well as dyno-calibrated 1D engine models enabled the gathering of invaluable data to design the proposed solution and compare it to the Original Equipment Manufacturer (OEM) version. Thanks to these processes, the comparison between the proposed design and the OEM one was not limited to the performance, and also included the manufacturing costs, which were calculated via Computer Aided Manufacturing (CAM) programs, with the limitation of using only Computer Numerical Control (CNC) machining for production. To conclude, the work showed a notable performance superiority of the proposed turbine in respect to the OEM one, despite a slightly higher estimated production cost.

Theoretical and Experimental Investigation of a Small-Scale, High-Speed, and Oil-Free Radial Anode Off-Gas Recirculation Fan for Solid Oxide Fuel Cell Systems

Abstract The Laboratory for Applied Mechanical Design (LAMD) designed, manufactured, and experimentally tested a novel recirculation fan for a 10 kWe solid oxide fuel cell (SOFC). The fan uses oil-free bearings, more specifically herringbone-grooved journal and spiral-grooved thrust gas bearings. The radial inducer-less fan with a tip diameter of 19.2 mm features backward-curved prismatic blades with constant height. Prior to coupling the recirculation fan with the SOFC, the fan was experimentally characterized with air at 200 °C. At the nominal point of 168 krpm, the measured inlet mass flow rate is 4.9 kgh–1, the total-to-total pressure rise 55 mbar, the isentropic total-to-total efficiency 55%, and the power 18.3 W. This paper compares the experimental data toward a computational fluid dynamic simulation of the full fan impeller and volute suggesting an excellent correlation at the nominal point which validates the numerical approach. However, the heat flows crossing the fan fluid domain have an increased effect at off-design conditions; thus, the experimental results need careful consideration. The fan backface leakage has negligible impact on the measurements.

Ранненеолитическое поселение Новопетровка III в Западном Приамурье и его хронология

В статье рассмотрена хронология неолитического памятника Новопетровка III в Западном Приамурье, установленная по данным радиоуглеродного датирования нагара на керамике. Новопетровская культура в целом, представленная памятниками Новопетровка I-III и Константиновка, исследованными в первой половине 1960-х гг., по результатам типологического анализа пластинчатой индустрии была отнесена к V (возможно, VI) — началу IV тыс. до н.э. Обзор данных по изготовлению призматических пластин с помощью отжимной техники показал, что хронологически пластинчатые индустрии появились на обширной территории Евразии в финале плейстоцена — начале голоцена и продолжали существовать в отдельных регионах вплоть до энеолита. Поэтому они могут служить лишь ориентиром в определении относительной хронологии памятников. С появлением в 1990-х гг. радиоуглеродных дат, полученных по органическому наполнителю в керамическом тесте и нагару на керамике с поселения Новопетровка II, новопетровская культура была удревнена до 15,5-10,8 тыс. л.н. (калиброванные значения). На основе сравнительного анализа новых радиоуглеродных дат, определенных по нагару, установлен возраст памятника Новопетровка III -9,0-9,5 тыс. лет. В связи с тем, что в археологическом материале с новопетровских поселений в рамках длительного периода изменений не выявлено, обозначена проблема хронологической оценки как новопетровской культуры в целом, так и ее отдельных памятников.