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To suppress the adverse effect of the gear windage phenomenon in the high-speed aeronautic industry, a shroud as an effective alternative strategy is usually to enclose gears to reduce the windage behaviors of high-speed gears. To deeply understand these no-load power losses, this paper proposes a new simulation methodology based on the Lattice Boltzmann method to study the windage losses of a shrouded spur gear and conducts a series of numerical studies. The models reproduce a shroud spur gear varying radial and axial clearances to evaluate the influence of casing walls on windage losses. The simulation results were then compared with experimental values, showing a satisfactory agreement. Furthermore, a torque containment factor integrating the air compressibility at high Mach numbers is introduced to represent the reduction in torque (windage power losses) for the shrouded gear compared to the free case, and the theoretical formulae for predicting windage power losses are further improved for better applicability as the tight shroud approaches the gear during the preliminary design stage. [ABSTRACT FROM AUTHOR]

In a recent thought-provoking analysis of the iconography on the exterior of the Mantle of Roger II (r. 1105–1154), the Norman ruler of Sicily and southern Italy, William Tronzo has advanced a compelling hypothesis suggesting that the Mantle may actually have been intended to serve as Roger's shroud. This article examines the intriguing but rarely discussed figured silks found within the Mantle's lining to assess whether their iconography aligns with Tronzo's hypothesis, which focuses primarily on the Mantle's exterior. The interior consists of a patchwork of silk fragments inserted into the famous garment as a relic-like lining, revealing a fascinating but often overlooked iconography: knotted serpents. Continuing an earlier practice, the repetition of the knotted serpent motif appears to have been deliberately employed to reinforce a beneficial effect, perhaps invoking the notion of unceasing, everlasting protection. This study contextualizes the richly multivalent symbol of the knotted serpent within the broader realm of southern Italian iconography, as well as its significance in the wider Mediterranean world and beyond. In particular, the research incorporates a fascinating discovery: a previously unnoticed silk fragment from the Afghan province of Samangan, now in the Al-Sabāh Collection in Kuwait. This fragment bears striking similarities to the textiles used in the cloak's lining, further enriching our understanding of its cultural and historical import. [ABSTRACT FROM AUTHOR]

To suppress the adverse effect of the gear windage phenomenon in the high-speed aeronautic industry, a shroud as an effective alternative strategy is usually to enclose gears to reduce the windage behaviors of high-speed gears. To deeply understand these no-load power losses, this paper proposes a new simulation methodology based on the Lattice Boltzmann method to study the windage losses of a shrouded spur gear and conducts a series of numerical studies. The models reproduce a shroud spur gear varying radial and axial clearances to evaluate the influence of casing walls on windage losses. The simulation results were then compared with experimental values, showing a satisfactory agreement. Furthermore, a torque containment factor integrating the air compressibility at high Mach numbers is introduced to represent the reduction in torque (windage power losses) for the shrouded gear compared to the free case, and the theoretical formulae for predicting windage power losses are further improved for better applicability as the tight shroud approaches the gear during the preliminary design stage.

The cooling fan is one of the important noise sources for new energy vehicles, and the research on its aerodynamic and aeroacoustic characteristics is of great help to improve the noise, vibration and harshness performance of new energy vehicles. However, most of these studies focus on the impeller, and little consideration has been given to the study of the shroud. Based on the coupling calculation method of large eddy simulation and the Ffowcs-Williams and Hawkings acoustics model, the aerodynamic and aeroacoustic characteristics in a cooling fan with the shroud are investigated at flow rates from 0.623 kg/s to 1.019 kg/s (where 0.865 kg/s is the flow rate corresponding to the best efficiency point). The accuracy of numerical simulation results is verified by the grid independence verification and the comparison of experimental data. Research shows that several large-scale vortex structures are observed in the clearance between the impeller and the shroud. The maximum peak-to-peak values of pressure fluctuation at different flow rates occur in the intermediate section or outlet section of the shroud. Although the shroud contributes relatively less to the far field noise, its different distribution may change the position of the maximum sound pressure level. The dominant frequency of pressure fluctuation equals the blade passage frequency (BPF) and the maximum SPL is around the BPF, both of which are independent of flow rates. The maximum SPL and the amplitude of the dominant frequency decrease as the flow rate increases. [ABSTRACT FROM AUTHOR]

Abstract In recent urban buildings, there is an interest in using wind turbines inside the buildings. Thus, the rotors of wind turbines are shrouded by the walls of the buildings. A design for using wind turbines in urban areas is to use shrouded turbines on the roof of a building. Since vertical axis wind turbines (VAWTs) with low environmental impacts are recommended for energy supply in urban areas, here, the interaction of two shrouded VAWTs has been studied numerically. Based on the effects of different shroud parts, the diffuser‐shrouded turbines are selected. The arrangement of diffuser‐shrouded VAWTs has been optimized using the response surface method optimization with the Kriging model. The optimization samples are chosen by the design of experiment method to reduce the number of simulations and increase optimization accuracy. The total power coefficient of the optimized cluster is 46.2% higher than the sum of the same individual diffuser‐shrouded turbines and 149.6% higher than the sum of individual bare VAWTs. The economic assessment shows that the levelized cost of energy of the optimized cluster of two diffuser‐shrouded VAWTs is reduced by about 40% compared to two bare VAWTs.

This research aims to analyze the performance of hydrokinetic turbines under yaw misalignment conditions using descriptive statistical methods on coefficient of power (Cp) data. Tests were conducted at water velocities of 0.7, 0.9, and 1.1 m/s for three types of turbine shrouds consisting of turbines without shrouds, turbines with two different types of shrouds, at yaw angles from 0° to 25° with 5° intervals. The study concludes that the performance of each turbine type is significantly influenced by the combination of water flow velocity and yaw angle. The diffuser type has the highest Cp value at every yaw angle, but its performance decreases with increasing yaw angle. The Blade type has poorer performance compared to the diffuser at every yaw angle and has the best performance at a combination of 1.1 m/s velocity and 5° yaw angle. Meanwhile, the shroud type has more stable performance and is not greatly affected by variations in velocity and yaw angle. Based on the analysis of changes in average Cp values with changes in yaw angle at V 0.7 m/s, all three turbine types experienced an increase in Cp value at a yaw angle of 5, with the shroud experiencing the most significant increase. At V 0.9 m/s, the diffuser and shroud types were able to maintain their average Cp values at every yaw angle, while the blade type decreased with increasing yaw angle and experienced a significant decrease at a yaw angle of 25. At V 1.1 m/s, the diffuser and blade types experienced a decrease in performance with every increase in yaw angle, but the shroud type was able to maintain the same Cp value and even experienced a significant increase at a yaw angle of 5.

In recent urban buildings, there is an interest in using wind turbines inside the buildings. Thus, the rotors of wind turbines are shrouded by the walls of the buildings. A design for using wind turbines in urban areas is to use shrouded turbines on the roof of a building. Since vertical axis wind turbines (VAWTs) with low environmental impacts are recommended for energy supply in urban areas, here, the interaction of two shrouded VAWTs has been studied numerically. Based on the effects of different shroud parts, the diffuser‐shrouded turbines are selected. The arrangement of diffuser‐shrouded VAWTs has been optimized using the response surface method optimization with the Kriging model. The optimization samples are chosen by the design of experiment method to reduce the number of simulations and increase optimization accuracy. The total power coefficient of the optimized cluster is 46.2% higher than the sum of the same individual diffuser‐shrouded turbines and 149.6% higher than the sum of individual bare VAWTs. The economic assessment shows that the levelized cost of energy of the optimized cluster of two diffuser‐shrouded VAWTs is reduced by about 40% compared to two bare VAWTs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Cycle of services of Novgorod Cathedral of the Holy Wisdom included singing services (ᾀσματική ἀκολουθία) after the practice of the Hagia Sophia in Constantinople. Its description is known since the 13th century from the Novgorod liturgical manuscripts. Since the end of 15th century the double-sided proskynesis icons has been an important integral part of singing service in Novgorod Cathedral. The unique complex of the images of the Saviour, Mother of God, saints, and the Bible scenes was created at this time. The complicated organization composition of the Novgorod series allowed to lay one icon in the church naos at festive day or to carry out all icons with images of saints to square near Cathedral during the rites of the New Year on September 1 and on Sunday of the Last Judgement. The icons replaced one another during the Holy Week. The Shroud with the embroidery image of dead Christ was carried out from altar and put on a table in the middle of naos at Holy Saturday. The icon Resurrection (Descent into Hell) replaced the Shroud at early morning of Resurrection Sunday. It was a real “mystery of images”. Богослужебный цикл в новгородском соборе Святой Софии включал знаменитые песенные последования (ᾀσματική ἀκολουθία) согласно Типикону Святой Софии в Константинополе. Их описания известны в новгородских литургических рукописях с XIII в. С конца XV в. важную роль в совершении песенных последований в Новгороде играли аналойные двусторонние иконы, уникальный комплекс которых с образами Спасителя, Богоматери, святых и библейских сюжетов был создан в это время. Организация серии позволяла как выкладывать на аналой в наосе храма в праздничный день одну икону, так и выносить иконы с образами святых на площадь близ Св. Софии в дни свершения действа Новолетия 1 сентября или в Неделю о Страшном суде. Иконы сменяли друг друга на аналое в Страстную седмицу. Плащаницу с шитым изображением мёртвого Христа выносили из алтаря на стол посредине наоса в Страстную Субботу, его сменяла икона «Воскресение (Сошествие во ад)» ранним утром Пасхального Воскресения. Это была подлинная «мистерия образов».

In plasma spraying, compared to other thermal spraying process variants, only a small part of the available energy is used to build up a coating. Another peculiarity of this process is the relatively strong oxidation of the sprayed metallic particles, caused by the high temperatures and turbulent flow of the plasma jet in combination with the ambient air. A promising solution for increasing energy efficiency is a solid shroud that surrounds the plasma jet and thus prevents air entrainments from mixing with the plasma gas. The primary goal of this study is to develop a numerical model to investigate the effect of an external fixed nozzle extension on the plasma jet as a shroud in case of a multi-arc plasma generator. To this end, the existing simulation models of the plasma jet from the previous works of the authors were extended to model a solid nozzle extension at the outlet of a three-arc plasma generator. The developed parametrized model can be used to optimize the geometry of the nozzle extension based on experimental measurements to adapt it to the flow conditions of the plasma jet. The results revealed that the plasma temperature could be increased using the nozzle extension even with relatively cold process parameters, thereby raising the energy efficiency to melt the particles in plasma spraying. [ABSTRACT FROM AUTHOR]

This research focuses on computational fluid dynamics modeling and experimental analysis of a shrouded wind turbine. A shroud turbine comprises a wind turbine with a flanged shroud encircling it for better wind energy utilization at low wind speed. The effects of diffuser shape and flange angle have been studied by performing flow field analysis in Ansys Fluent for better utilization and condensing of the shroud size. The CFD analysis shows that a cycloid diffuser shape gives 7% more velocity than a straight shape. In addition, the optimum flange angle for a cycloid diffuser is +10°, while compared with the normal flange angle, the optimal flange angle has increased velocity and power by 4.83% and 15%, respectively. This increment is due to the variation in the magnitude of vortex generation behind the flange. Besides, the performance of the proposed 3D, shrouded, and unshrouded wind turbines was numerically analyzed, and a prototype model for the proposed wind turbines was manufactured and tested. The simulation and experimental results agree and lay within the acceptable range. Compared with an unshrouded wind turbine with a similar swept area and wind speed, the shrouded wind turbine increased velocity and power by 1.58 and 5, respectively. This increase in speed and power makes the shrouded turbine suitable for application in low wind speed areas. Moreover, it can be helpful in sparsely populated off-grid areas to generate electricity by being mounted on rooftops.

Wind-lens turbines (WLTs) exhibit the prospect of a higher output power and more suitability for urban areas in comparison to bare wind turbines. The wind-lens typically comprises a diffuser shroud coupled with a flange appended to the exit periphery of the shroud. Wind-lenses can boost the velocity of the incoming wind through the turbine rotor owing to the creation of a low-pressure zone downstream the flanged diffuser. In this paper, the aerodynamic performance of the wind-lens is computationally assessed using high-fidelity transient CFD simulations for shrouds with different profiles, aiming to assess the effect of change of some design parameters such as length, area ratio and flange height of the diffuser shroud on the power augmentation. The power coefficient (Cp)is calculated by solving the URANS equations with the aid of the SST k–ω model. Furthermore, comparisons with experimental data for validation are accomplished to prove that the proposed methodology could be able to precisely predict the aerodynamic behavior of the wind-lens turbine. The results affirm that wind-lens with cycloidal profile yield an augmentation of about 58% increase in power coefficient compared to bare wind turbine of the same rotor swept-area. It is also emphasized that diffusers (cycloid type) of small length could achieve a twice increase in power coefficient while maintaining large flange heights. [ABSTRACT FROM AUTHOR]

Despite recognizing the importance of cooling within gear systems, there is a lack of clear design guidelines to minimize churning losses while enhancing heat dissipation performance. This study proposes a reliable approach to modeling using a steady-state approximation methodology based on heat-flow coupling for multiphysics around shrouded gears. Computational analyses reveal a distinctive multiphase flow induced by pressure gradients. The efficacy of the proposed methodology is empirically verified through its ability to characterize lubricant distribution and churning losses in splash lubrication systems. Furthermore, an innovative shroud optimization framework is introduced to regulate friction and collision between fluid particles and gear surfaces, enhancing splash lubrication performance. A genetic algorithm is employed within this framework to obtain shroud configurations for gears with a higher wall heat transfer coefficient (WHTC) and lower resistance torque. Implementing the optimal shroud design achieves a trade-off in terms of a notable 13.7% reduction in resistance torque alongside 11.6% and 4% increments in WHTC for the tooth root face and tooth face, respectively. This signifies enhanced reliability in multiphysics governing gearbox functionality, thereby providing valuable guidance for the design of shrouded gear systems. [Display omitted] • A steady-state approximation modeling methodology based on heat-flow coupling. • The evolution of the resistance torque and wall heat transfer coefficient of the gear with different shroud configurations. • A shroud optimization framework that overcomes the uncertainty of multiple physics. • Reduction in resistance torque by 13.7%. • Improving the wall heat transfer coefficient of the tooth root by 11.6%. [ABSTRACT FROM AUTHOR]

Copyright of Anagnórisis: Revista de Investigación Teatral is the property of Anagnorisis: Revista de Investigacion Teatral and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the increasing speed of aviation gear, windage loss has been the main component of power loss. Reducing windage is of great significance to improving the transmission efficiency of aviation spiral bevel gear. Firstly, the calculation model of enclosed spiral bevel gear was established, and the basic physical mechanism of windage power loss was illustrated by numerical simulation, so as to obtain the mechanical and energy characteristics of windage loss. Then, the influence of the geometry and clearance parameters of the shroud on the windage loss was studied by orthogonal test, variance analysis and optimization design. The mechanism of the shroud to reduce the windage loss under the multi-factors was also studied, and their interaction was obtained. The results show that the tooth surface clearance, heel clearance and meshing opening are significant factors, and the most significant factor is the heel clearance. The non-significant factor is the interaction of each factor. The least significant factor is the toe clearance. In other words, the windage power loss can be reduced to the greatest extent by simultaneously reducing the meshing opening of the shroud and the clearance value between shroud and the surface of the gear. Finally, based on the mechanism of reducing windage loss of shroud, the optimization design principle affecting the structural performance of shroud is put forward, which provides theoretical guidance for the practical application of shroud in windage reduction engineering. [ABSTRACT FROM AUTHOR]

Featured Application: This study contributes to the design of mixed inflow turbines to improve their performance in internal combustion engines. The choice of blades for mixed turbines is to achieve the required deflection with minimal losses. In addition, it is necessary that the blade functions without a detachment in a wide area outside the nominal operating point of the machine. In the blade profile study, it is required to satisfy the conditions relating to fluid mechanics and those relating to the possibility of realization of construction. The work carried out presents the effect of the blade deviation angle on the geometric blade shape and the performance of the mixed inflow turbine on keeping the same rotor casing in order to improve its performances. It was remarked that the efficiency is proportional to the deviation angle's increase, but the rotor became heavy. It has been determined that the effect of the blade deviation angle on mixed inflow performances decreases dramatically starting from the angle −20° for a 100% of machine load. It was urged to avoid relying on angles greater than −20 as values for blade deviation angles. The study noted that the maximum obtained in the output work and power is related to the highest the efficiency for a specific optimum design case (−35° of deviation blade angle) due to the increase in the contact surface between the blade and the fluid, but the problem is that the rotor gets a little heavy (4.37% weight gain). Among recommendations, attention was given to the more significant absolute exit kinetic energies, for values of deviation blade angle between -10° and −20°, where an exhaust diffuser is recommended to use to recover a part of it into a greater expansion ratio. These simulation results were obtained using a CFD calculation code-named CFX.15. This code allowed for the resolution of the averaged dynamic equations governing the stationary, compressible, and viscous internal flow. [ABSTRACT FROM AUTHOR]

The shroud is a key component of the frost-free refrigerator and its geometric parameters have great influence on the aerodynamic performance of the whole system. Previous researches mainly focused on the effect of other components, such as the fan, shelves, or plate-evaporator. In this paper, the influence of the shroud with multi-outlets on the flow distributions of a frost-free refrigerator is studied thoroughly with the help of Computational Fluid Dynamics (CFD) tools. A 1/2 3-D CFD model is developed, where the verification of turbulence models and mesh independence tests are performed by comparing the mass flow rate obtained by different model configurations. The standard k-epsilon is deemed as the most suitable turbulence model choice and a mesh with Fine level is considered as mesh independence. To obtain the boundaries of the developed CFD model, an airflow velocity test rig is built and constructed. To convert the measured data to CFD model, Structural Response Vector (SRV) method is implemented for velocity profile fitting, and the fitted surface is assigned by User Defined Functions (UDF) macros in simulations. A series of simulations are carried out with the developed model, and the results indicates that no streamline in the middle two cavities of the original freezer compartment and the airflow velocities at the three outlets of the investigated shroud show a certain difference. To optimize the flow distribution, the agent model based on the BP neural network is established, in which four critical parameters of the shroud are adopted as design variables. The results show that the velocity streamlines in the middle two cavities are significantly increased after optimization and the value of the mean square error model constructed in optimization has a reduction of 61.09% compared with the original design.

This research focuses on computational fluid dynamics modeling and experimental analysis of a shrouded wind turbine. A shroud turbine comprises a wind turbine with a flanged shroud encircling it for better wind energy utili- zation at low wind speed. The effects of diffuser shape and flange angle have been studied by performing flow field analysis in Ansys Fluent for better utiliza- tion and condensing of the shroud size. The CFD analysis shows that a cycloid diffuser shape gives 7% more velocity than a straight shape. In addition, the optimum flange angle for a cycloid diffuser is +10°, while compared with the normal flange angle, the optimal flange angle has increased velocity and power by 4.83% and 15%, respectively. This increment is due to the variation in the magnitude of vortex generation behind the flange. Besides, the performance of the proposed 3D, shrouded, and unshrouded wind turbines was numerically analyzed, and a prototype model for the proposed wind turbines was manufac- tured and tested. The simulation and experimental results agree and lay within the acceptable range. Compared with an unshrouded wind turbine with a similar swept area and wind speed, the shrouded wind turbine increased velocity and power by 1.58 and 5, respectively. This increase in speed and power makes the shrouded turbine suitable for application in low wind speed areas. Moreover, it can be helpful in sparsely populated off-grid areas to generate electricity by being mounted on rooftops. [ABSTRACT FROM AUTHOR]

In order to prevent molten steel reoxidation in the tundish during continuous casting, argon injection into the shroud is applied. The injected argon bubbles in molten steel may change the molten steel flow pattern in the tundish. Consequently, the ratios of dead zone, plunger zone and well-mixed zone would change. Also, the motion of inclusions in the molten steel of tundish would change resulting from argon injection. The current word developed a coupling multiphase flow mathematical model. Basing on the developed model, the present work has researched the influences of argon injection on the molten steel flow pattern, inclusion motion characteristics in the tundish. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is well known that a shroud placed around a wind turbine can increase its power coefficient, but it brings complex mechanisms by which the shroud alters the flow passing through the rotor. Such mechanisms impose numerical challenges, as the shrouded turbines present nonlinear behavior in the wake. This paper deals with a comprehensive analysis of tip vortex trajectory in shrouded wind turbines using Reynolds Averaged Navier–Stokes numerical solutions. The analysis includes aerodynamic performance and vortex characteristics of the whole wind turbine. The Multiple Reference Frame is used on a high-order unstructured compressible solver to study both, isolated and shrouded rotor. The NREL Phase VI Unsteady Aerodynamic Experiment rotor is used as a test case. The accuracy of results for wind speeds between 7 and 25 m s − 1 is discussed. Overall, good agreement is achieved between the computed pressure distributions and the experimental reference values. At stalled blade, more efforts are needed to improve numerical solutions, especially for integrated load quantities. The vortex structure is examined, showing that shroud impacts tip vortex trajectory by the increase of the axial induced velocity at the rotor plane. This result, demonstrates that the classical Prandtl tip loss is not accurate for shrouded turbine analysis, and modern finite blade functions are needed. The influence of the flow conditions on the tip vortex trajectory, flow separation and shroud interaction are also discussed. • Tip vortex trajectory of the NREL Phase Vi. • Use of a simplified Multiple Reference Frame model with open-source high-order CFD solver, avoiding conformal interface complexities and enabling efficient shrouded turbine simulation. • Accurate and efficient computation of the integrated loads on the wind turbine. • Unprecedented perspective into profoundly altered tip vortex trajectory behavior within shrouded turbines using validated higher-order framework. • Study of the interaction between the tip vortex and shroud's boundary layer. [ABSTRACT FROM AUTHOR]

In the current study, effects of two different underhood geometry modifications namely; fan position relative to shroud and fan tip clearance, on airflow through an agricultural tractor engine cooling system are investigated by utilizing CFD modeling. For the characterization of each modification, the underhood components are reduced to a domain of cooling systems including only fan, shroud, and radiator that allows saving in computational time and cost. The models are validated using a custom designed underhood flow setup, where hotwire velocity measurements at proximity to the radiator are conducted. The mass flow rate and the uniformity of the airflow through the radiator are quantified as performance parameters. For the former modification, position of fan relative to shroud, the computations are performed for the percentages of fan projection into shroud (FPiS) varying from 78% to 0% at fan rotational speeds of 2060 and 2800 rpm. The optimum fan location is found to be around 56–60% for both rotational speeds that leads 8% increase in mass flow rate compared with the pre-design location of 74%. In addition, a noticeable reduction in the relative magnitude of the RMS velocity through the radiator is obtained for the moderate FPiS values. For the latter modification, fan tip clearance, the computations are performed for the tip clearance values varying from 5.25to 12 mm at a fan rotational speed of 2060 rpm. As the tip clearance decreases up to 6 mm, air mass flow rate can be improved by 7%. However, further reduction in tip clearance does not improve the air mass flow rate instead it decreases, suggesting an optimum tip clearance value. The results suggest that the proper geometrical modifications in engine cooling systems might induce significant improvement in the aforementioned performance indicators.

Variable-pitch multifinned seals (VPMS) have not hitherto found wide use in the steam turbines produced in Russia, although they are quite often used outside of Russia. In modernizing the existing and designing new steam turbines, rotor blades with an integrally machined shroud are used, which opens the possibility to manufacture multirow peripheral seals. In this connection, the question about selecting the optimal VPMS configuration becomes of important practical significance. The results obtained in this study made it possible to experimentally estimate the extent to which different combination of fin pitches on the rotor and stator influence the VPMS discharge characteristics and to elaborate practical recommendations on using them. The minimal leak flow was recorded for the VPMS models with a 2-mm-wide pitch on the rotor. Comparative experimental investigations of VPMS models with 3- and 4-mm-wide spacers on the rotor and 4- and 5-mm-wide spacers on the stator were carried out as applied to the shroud seals of large-capacity steam turbines. The model pair with the 4- and 5-mm-wide spacers on the rotor and stator, i.e., with the pitches equal to 4.8 and 5.8 mm on the rotor and stator, respectively, can be regarded as the most optimal of those investigated in this work. It has been shown experimentally that, with all other things being equal, the leak in VPMSs is by 22–25% smaller than it is in straight-flow seals. By using VPMS, it becomes possible to avoid rubbing of the rotor against the stator under the conditions of relative radial and axial rotor displacements in transient modes of operation. In addition, the aerodynamic forces in VPMS able to excite a low-frequency shaft line self-oscillation are approximately equal to 60% of the similar forces occurring in the conventional radial clearance seals. In view of this circumstance, VPMS can be recommended for use instead of the standard tip shroud seals in the high- and intermediate-pressure cylinders in new and modernized steam turbines. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Research in Humanities is the property of Tarbiat Modares University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the increasing speed of aviation gear, windage loss has been the main component of power loss. Reducing windage is of great significance to improving the transmission efficiency of aviation spiral bevel gear. Firstly, the calculation model of enclosed spiral bevel gear was established, and the basic physical mechanism of windage power loss was illustrated by numerical simulation, so as to obtain the mechanical and energy characteristics of windage loss. Then, the influence of the geometry and clearance parameters of the shroud on the windage loss was studied by orthogonal test, variance analysis and optimization design. The mechanism of the shroud to reduce the windage loss under the multi-factors was also studied, and their interaction was obtained. The results show that the tooth surface clearance, heel clearance and meshing opening are significant factors, and the most significant factor is the heel clearance. The non-significant factor is the interaction of each factor. The least significant factor is the toe clearance. In other words, the windage power loss can be reduced to the greatest extent by simultaneously reducing the meshing opening of the shroud and the clearance value between shroud and the surface of the gear. Finally, based on the mechanism of reducing windage loss of shroud, the optimization design principle affecting the structural performance of shroud is put forward, which provides theoretical guidance for the practical application of shroud in windage reduction engineering.

The choice of blades for mixed turbines is to achieve the required deflection with minimal losses. In addition, it is necessary that the blade functions without a detachment in a wide area outside the nominal operating point of the machine. In the blade profile study, it is required to satisfy the conditions relating to fluid mechanics and those relating to the possibility of realization of construction. The work carried out presents the effect of the blade deviation angle on the geometric blade shape and the performance of the mixed inflow turbine on keeping the same rotor casing in order to improve its performances. It was remarked that the efficiency is proportional to the deviation angle’s increase, but the rotor became heavy. It has been determined that the effect of the blade deviation angle on mixed inflow performances decreases dramatically starting from the angle −20° for a 100% of machine load. It was urged to avoid relying on angles greater than −20 as values for blade deviation angles. The study noted that the maximum obtained in the output work and power is related to the highest the efficiency for a specific optimum design case (−35° of deviation blade angle) due to the increase in the contact surface between the blade and the fluid, but the problem is that the rotor gets a little heavy (4.37% weight gain). Among recommendations, attention was given to the more significant absolute exit kinetic energies, for values of deviation blade angle between -10° and −20°, where an exhaust diffuser is recommended to use to recover a part of it into a greater expansion ratio. These simulation results were obtained using a CFD calculation code-named CFX.15. This code allowed for the resolution of the averaged dynamic equations governing the stationary, compressible, and viscous internal flow.

Nowadays, after more than twelve decades of studies involving many scientists from all over the world, we do not know the originary chemistry of the Shroud of Turin. This state of affairs is due to the uncertainty between two possibilities. The first one, deduced by Heller and Adler, asserts that the surface chemistry is linen cellulose structure. The two scientists have obtained this result by microanalysis of the samples extracted from the Linen of Turin. The second one, deduced by Rogers and subsequently studied with Arnoldi, supports the hypothesis that the linen threads were, in origin, covered with a thin layer of impurities. Also this result has been experimentally obtained. In fact, by microchemical tests, using iodine on thread pieces of the Shroud linen, it was detected the starch impurities presence. This study is an attempt to analyze the Rogers' hypothesis: a Maillard reaction between amines (nitrogen compound with a free -NH2 group), coming through the corpse wrapped in the Linen of Turin and reduced sugars, due to the manufacturing procedure, present on the surface of the above linen cloth. Therefore, as it has already affirmed, we have two different visions. However, we must take also into account that the second one hypothesis needs, at same time, the presence of amines and the absence of aromas and/or burial ointments. The aim of this our study is to see if the above hypothesis (the one of Rogers with Arnoldi) is able to yield on the linen a color distribution characterized by a I(z) correlation between the intensity of color and the cloth-body distance, as it occurs to the Shroud of Turin. [ABSTRACT FROM AUTHOR]

Based on Islamic era sources, inscribed robes were one of the valuable art works during the Ale-Buyid period that were gifted to courtiers in official ceremonies as a sign of honor for their loyalty. These robes normally contained the name of the ruler. In the Ale-Buyid period, a combination of both Shi'a and Iranian-Sasanian led to the creation of a new style of art. From the remains of that period, number of textiles with inscriptions was discovered from two enclosures of Broj-e Nagharekhane and Bibi Shahrbanu in Ray. According to archaeological reports, the scripted textiles were used as shrouds or to cover graves. The inscriptions are in both plain and ornamental Kufic styles and in most of the cases, beside its function to convey a massage, had decorative functions too. Based on 25 scripted textile pieces from Ale-Buyid period which mostly were discovered from Ray, this research attempts to reveal the meaning and also the literature sources of the inscriptions. The data has been collected through library studies. This research shows that the texts contain prayers, ethical massage and some poems from Arab poets from the first Hijri to the Ale-Buyid period. In some cases, embroidery has changed the shape of the letters to create a rhythmic pattern in the text and for this reason; the text is illegible or contains a visual or written error. This shows that writing was as important as its content. Most of the fabrics obtained based on the content were robes, and the content of the inscriptions often had an individual audience and a prayer sentence. [ABSTRACT FROM AUTHOR]

The shroud is a key component of the frost-free refrigerator and its geometric parameters have great influence on the aerodynamic performance of the whole system. Previous researches mainly focused on the effect of other components, such as the fan, shelves, or plate-evaporator. In this paper, the influence of the shroud with multi-outlets on the flow distributions of a frost-free refrigerator is studied thoroughly with the help of Computational Fluid Dynamics (CFD) tools. A 1/2 3-D CFD model is developed, where the verification of turbulence models and mesh independence tests are performed by comparing the mass flow rate obtained by different model configurations. The standard k-epsilon is deemed as the most suitable turbulence model choice and a mesh with Fine level is considered as mesh independence. To obtain the boundaries of the developed CFD model, an airflow velocity test rig is built and constructed. To convert the measured data to CFD model, Structural Response Vector (SRV) method is implemented for velocity profile fitting, and the fitted surface is assigned by User Defined Functions (UDF) macros in simulations. A series of simulations are carried out with the developed model, and the results indicates that no streamline in the middle two cavities of the original freezer compartment and the airflow velocities at the three outlets of the investigated shroud show a certain difference. To optimize the flow distribution, the agent model based on the BP neural network is established, in which four critical parameters of the shroud are adopted as design variables. The results show that the velocity streamlines in the middle two cavities are significantly increased after optimization and the value of the mean square error model constructed in optimization has a reduction of 61.09% compared with the original design. [ABSTRACT FROM AUTHOR]

Banville’s latest trilogy Eclipse, Shroud, and Ancient Light forms an interconnected web of narratives that aptly dramatizes Banville’s fictional investigation of subjectivity and otherness. The “other” in these narratives is consistently a female other on whom the narrators bestow a multitude of roles in their narcissist quests for authenticity. The “woman” is represented simultaneously as an enigma, the site of “truth”, the guarantor of the narrators’ authentic self, and the screen onto which the protagonists aim to inscribe their aesthetic signatures. This paper proposes to read these figurations in close relation with the theoretical undertone with which Banville engages throughout his philosophically imbued meta-fiction. It specifically addresses the way in which the figure of the “woman” becomes entangled with Paul de Man’s elaborations on the “ontological crisis” in Romanticism as well as Friedrich Nietzsche’s aesthetics of the “surface”. Banville’s fictional engagement with these thinkers, I claim, offers a way to read the narrators’ ethical failure with regards to the key female characters as an aesthetic critique of ideology.

The downwind rotor configuration provides a structural advantage compared with an upwind design. However, tower shadow has long been a concern for downwind systems. The tower shadow negatively affects the blade by introducing a load impulse during the wake passage. An aerodynamic fairing could shroud the tower reducing the wake. However, there is no clear consensus on the importance of a tower shadow for utility‐scale wind turbines. Simulations were conducted in FAST to determine the general parameters that influence the importance of the tower shadow effect for the differently sized wind turbines. The lock number of the blade was a significant driving quantity. Lower lock numbers (typical of small‐scale wind turbines) lead to greater relative fatigue damage from tower shadow effects. It was determined that a fairing is very helpful for small‐scale wind turbines operating in a low‐turbulence environment (such as a subscale wind tunnel test). However, the tower shadow increased the damage equivalent loading on an extreme scale blade by less than 5% in a turbulent environment. These results indicate that the cost of a tower fairing is likely unnecessary for utility‐scale wind turbines in operation. [ABSTRACT FROM AUTHOR]

To achieve higher efficiency and performance, a modern gas turbine withstands the extremely high thermal environment. In the turbine endwall passage, a high and non-uniform heat transfer appears due to various secondary flow. The purge flow injected through the upstream slot between the stationary and rotating pars can thermally protect the endwall surface by forming air film layer on it. However, since an excessive amount of purge flow reduce the system efficiency, it is needed to effectively inject the purge flow with a limited amount. Accordingly, in the present study, the effect of purge slot exit shape on the film cooling effectiveness (hereby FCE) of a shroud surface was discussed. As nondimensional design parameters of the purge slot, L/W s , R W /W s , and R L /W s were defined, representing the geometric features: the slot width (W s), the fillet radius at the windward side (R W) and fillet radius at the leeward side (R L) of slot exit, respectively. The measurement of the FCE was performed in a five-blade linear cascade rig using the PSP (Pressure sensitive paint) technique. The results showed that the FCE increased for wider slot width at a given blowing ratio condition. In addition, the fillet radius at the windward side (R W) has a negative effect on the FCE regardless of blowing ratio condition since the purge flow was easily disturbed by the accelerated mainstream injection. On the other hand, the Case 7 with the R W /W s = 0.9 showed 5.1 % of the improvement of FCE at a higher blowing ratio M = 0.25 compared with the Case 2 with R W /W s = 0, which represents the sharp edge at the windward side of the slot exit. • Film cooling of a gas turbine shroud was studied using pressure sensitive paint technique. • Effects of purge slot exit shape on the film cooling effectiveness were examined. • A narrower slot width was beneficial for higher film cooling effectiveness. • A fillet at the windward side has a negative effect on film cooling effectiveness. • Small radius filler at the leeward side induced higher film cooling effectiveness. [ABSTRACT FROM AUTHOR]

Small wind turbines have a lot of promise in areas that are remote from the power grid. For such small-scale applications, such as off-grid electricity, a spiral wind turbine (SWT), a novel type of horizontal-axis wind turbine, may be employed. Placing wind turbines within a duct is one potential method for increasing the efficiency of wind energy harvesting in low-wind urban locations. In this work, a shroud with a flange at its outlet is created using an optimization approach that attempts to maximize the coefficient of power ( C P ), which improves SWT performance. An evolutionary algorithm over a Kriging interpolative model serves as the optimizer in use. The shroud's shape is determined using a series of straight lines. Using the commercial code program ANSYS-FLUENT, the Reynolds-averaged Navier-Stokes (RANS) equations are solved along with the SST k–ω turbulence model to determine the turbine C P . The computational results are validated and confirmed with previously published results. The optimal shroud design introduced significant improvements in the C P when applied to the SWT , resulting in a maximum C P of 0.967 (at λ = 3.25), which is 3.6 times the maximum C P of the bare SWT ( C P = 0.2668 at λ = 2.5). • The seashell-shaped spiral wind turbine (ASWT) performance is improved in this work by designing a shroud with a flange. • An optimization strategy aims to maximize the power coefficient ( C P ). • The employed optimizer is an Evolutionary Algorithm over a Kriging interpolation model. • Numerical investigation is performed by solving 3D Reynolds Navier–Stokes equations. • Results indicated that the optimal shrouded ASWT exhibits a maximum C P -value of 0.967. [ABSTRACT FROM AUTHOR]

This paper proposed a research method for secondary design and parametric analysis of the contraction section of the shroud to improve the flow-gathering effect of horizontal axis tidal current turbines. By comparing the velocity ratio, drag coefficient, and flow field stability of the nine different shroud profile types, a conclusion was drawn that the hydrodynamic performance of the exponential (Type-A) shroud is best. On this basis, the primary parametric analysis of the A profile type shroud is carried out by changing the contraction ratio of the shroud's contraction section to divide the profile into three parts. The results show that the vertical flange inhibits the flow-gathering effect of the shroud, so the secondary parametric analysis is proceeded by removing the flange and changing the flange inclination angle, respectively. At the contraction ratio of 6/8, the flow-gathering effect of each shroud is best, among which the hydrodynamic performance of Type-ABL-6-85° shroud with the flange inclination angle of 85° is best. The maximum power coefficient (C pmax) is 43.20%, which is 31.59% higher than that with Type-A shroud when the tip speed ratio is 1.5. Therefore, it can be considered that the combined profile type of the shroud contraction section has a better flow-gathering effect than the single profile type. • A new profile of exponential shroud is introduced to improve flow-gathering effect. • The shroud is designed by a two-stage optimization method. • The hydrodynamic performance of the shroud is analyzed under different contraction ratios. • The shroud shows a better flow-gathering effect by using combined profile types. [ABSTRACT FROM AUTHOR]

In this study, effect of shroud on dynamic characteristics of a rotating multi blade system is investigated. The main aim of this study is to investigate the effect of shroud stiffness and shroud configuration on the system natural frequency. For this purpose, natural frequencies of various systems (in terms of the position, where the blade is connected to the shroud and number of blades, which are connected together with a shroud) via different degrees of shroud stiffness and different configurations of shroud have been compared to show how this parameters affect the natural frequencies of the system. In this study, the shrouds have been considered as the discrete springs with corresponding stiffness values. The vibration frequency characteristics have been analyzed, using assumed mode method along with Hamilton’s law. Since in multi blade systems such as turbines it is crusial to keep the system working frequencies far away from natural frequencies (in order to prevent the resonance phenomenon), based on the results of this paper, it is shown how the parameters of shroud can remove the natural frequencies associated with some of the modes of the system from the work area. [ABSTRACT FROM AUTHOR]

Painted surfaces are useful for thermal control in spacecrafts. Knowledge of emissivity of such painted surfaces over the range of working temperatures is critical in eventually deciding the adequacy of any thermal control strategy. In view of the very low temperatures involved and also because of the variation of temperature in the spacecraft, the emissivity is invariably a function of temperature, which makes its determination formidable and challenging. A "straight forward" technique to measure or estimate emissivity at cryogenic temperatures is to use a steady state calorimetric technique coupled with energy balance. This involves heat transfer by radiation under steady state conditions between an evacuated cryogenic shroud and a heated test sample, centrally suspended inside the shroud. Apart from the heat supplied, knowledge of temperatures, the internal surface area and emissivity of the shroud is required to estimate the emissivity of the unknown test sample. The view factor can be taken care of, if the test sample is much smaller compared to the shroud, resulting in a view factor of 1 between the sample and the shroud. The key difficulty associated with the seemingly simple procedure is the shroud emissivity, which is often unknown at very low cryogenic temperatures. This paper presents a novel experimental approach for the in-situ estimation of cryogenic shroud (coated with ECP2200 paint) emissivity using measured data from experiments on a plane surface substrate and a cavity surface substrate (a surface with an array of hexagonal cavities) coated with an unknown test sample (Aeroglaze Z307 paint). For an average cryogenic shroud temperature of 32.53 K, the shroud emissivity has been estimated to be 0.355. Following this, the emissivities of the plane surface substrate and the cavity surface substrate coated with Aeroglaze Z307 are estimated. The associated measurement uncertainties are systematically quantified and presented. [ABSTRACT FROM AUTHOR]

Radiocarbon dating and scanning electron microscopy analyses were used to determine the age and conservation state of a palm mat made with hard fibers and a cotton shroud found in a funerary bundle of Zimapán Hidalgo, México. The fibers were also treated with an innovative treatment of chitosan and polypropylene glycol. The treatment was analyzed with a scanning electron microscopy and radiocarbon dating was applied to the treated fibers. The radiocarbon dating showed dates of 1022 a 1206 cal d.C therefore the textiles are prehispanic, and the treated fibers showed an early date (72-418 cal d.C.). This difference could be explained from the reservoir effect in the marine organisms because the chitosan is obtained from the chitin of crustacean's exoskeletons. The analysis also showed that the treatment for the fibers was effective because the fibers gained consolidation, flexibilization and also microorganisms were killed and removed. [ABSTRACT FROM AUTHOR]

Abstract Wind energy is anticipated to play a vital role to fulfill the worldwide energy requirements, whereas existing bare wind turbines can convert only a fraction of flow energy into electricity. To bridge the gap between the escalating demand and the generation capability, we propose a shrouded-twin-rotor turbine design, whose power coefficient exceeds the Betz-Joukowsky limit. We analyze the flow through the wind turbine assembly, using the actuator disk theory, and estimate the power output for a pair of rotor-loading coefficients. We find the existence of two regimes in which the proposed design performs better than the single-rotor configuration: (a) a turbine-turbine mode where both rotors work as turbines and (b) a turbine-fan mode where one rotor is a turbine while the other is a fan- an idea proposed by Betz (A. Betz, Wind-Energie und ihre Ausnutzung durch Windmühlen, Vandenhoeck, 1926). Both modes enable achieving maximum power for multiple combinations of the loading coefficient pair. Moreover, power output depends solely on a single parameter, defined using the area weighted sum of the loading coefficients. We derive the optimum performance criterion and present the effects of the shroud geometry, back pressure, and flow-efficiency parameters on the power output and the performance envelope. Highlights • Actuator disc theory has been applied to a novel shrouded-twin-rotor wind turbine. • A turbine-turbine and a new turbine-fan operational mode have been identified. • The power coefficient exceeds the Betz-Joukowsky limit for both operational modes. • Identify the parameter space where the power output exceeds single-rotor turbine. • Dominant parameters are back-pressure, throat area and nozzle viscous losses. [ABSTRACT FROM AUTHOR]