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Статті в журналах з теми "Bearing chamber":
1
Nazin, Vladimir. "Identifying the influence of design parameters of single-chamber hydrostatic bearing of fuel pump on its main characteristics." Eastern-European Journal of Enterprise Technologies 1, no. 7 (127) (February 28, 2024): 30–36. http://dx.doi.org/10.15587/1729-4061.2024.298646.
Анотація:
The object of this study is hydrostatic processes in the fluid friction bearings of gear-type aviation fuel pumps. The problem of the influence of the design parameters of a single-chamber hydrostatic bearing on its main characteristics was solved. The main characteristics were considered to be the load-bearing capacity and the flow rate of the working fluid. When determining the main characteristics of a single-chamber hydrostatic bearing, the Reynolds and flow balance equations were solved jointly. The resulting diagram of pressure distribution over the working surface of the bearing was used to determine the main characteristics. The influence of the clearance, nozzle diameter, and chamber width on the load-bearing capacity and working fluid flow of a single-chamber hydrostatic bearing was studied. It has been established that as the gap increases, the load-bearing capacity of a single-chamber bearing decreases, and the flow rate of the working fluid increases. As the nozzle diameter increases, the bearing's load-bearing capacity increases. Increasing the width of the chambers leads to an increase in the load-bearing capacity and flow of working fluid through the bearing. When the gap increases from 0.0125 mm to 0.0425 mm, the bearing capacity decreases by 1.156 times. The flow rate of working fluid through the bearing increases by 1.4 times. With an increase in the nozzle diameter from 1.5 mm to 3 mm, the bearing capacity increases slightly by approximately 1.02 times. Increasing the width of the chambers from 4 mm to 8 mm increases the load-bearing capacity by 1.29 times and increases the flow rate of working fluid by 1.4 times. The results show that a single-chamber hydrostatic bearing can provide the required load-bearing capacity by selecting design parameters. The given mathematical dependences could be used for practical calculations of single-chamber hydrostatic bearings
2
Flouros, Michael. "The Impact of Oil and Sealing Air Flow, Chamber Pressure, Rotor Speed, and Axial Load on the Power Consumption in an Aeroengine Bearing Chamber." Journal of Engineering for Gas Turbines and Power 127, no. 1 (January 1, 2005): 182–86. http://dx.doi.org/10.1115/1.1805009.
Анотація:
Trends in aircraft engines have dictated high speed rolling element bearings up to 3 million DN or more with the consequence of having high amounts of heat rejection in the bearing chambers and high oil scavenge temperatures. A parametric study on the bearing power consumption has been performed with a 124 mm pitch circle diameter (PCD) ball bearing in a bearing chamber that has been adapted from the RB199 turbofan engine DN∼2×106. The operating parameters such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed have been varied in order to assess the impact on the power consumption. This work is the first part of a survey aiming to reduce power losses in bearing chambers. In the first part, the parameters affecting the power losses are identified and evaluated.
3
Flouros, Michael. "Reduction of Power Losses in Bearing Chambers Using Porous Screens Surrounding a Ball Bearing." Journal of Engineering for Gas Turbines and Power 128, no. 1 (May 1, 2005): 178–82. http://dx.doi.org/10.1115/1.1995769.
Анотація:
Trends in aircraft engine design have caused an increase in mechanical stress requirements for rolling bearings. Consequently, a high amount of heat is rejected, which results in high oil scavenge temperatures. An RB199 turbofan bearing and its associated chamber were modified to carry out a survey aiming to reduce power losses in bearing chambers. The test bearing was a 124 mm PCD ball bearing with a split inner ring employing under-race lubrication by two individual jets. The survey was carried out in two parts. In the first part, the investigations were focused on the impact on the power losses in the bearing chamber of the operating parameters, such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed. In the second part, the investigations focused on the reduction of the dwell time of the air and oil mixture in the bearing compartment and its impact on the power losses. In this part, porous screens were introduced around the bearing. These screens would aid the oil to flow out of the compartment and reduce droplet-droplet interactions as well as droplet-bearing chamber wall interactions. The performance of the screens was evaluated by torque measurements. A high-speed camera was used to visualize the flow in the chamber. Considerable reduction in power loss was achieved. This work is part of the European Research programme GROWTH ATOS (Advanced Transmission and Oil Systems).
4
Gorse, P., S. Busam, and K. Dullenkopf. "Influence of Operating Condition and Geometry on the Oil Film Thickness in Aeroengine Bearing Chambers." Journal of Engineering for Gas Turbines and Power 128, no. 1 (March 1, 2004): 103–10. http://dx.doi.org/10.1115/1.1924485.
Анотація:
Increasing the efficiency of modern jet engines does not only imply to the mainstream but also to the secondary air and oil system. Within the oil system the bearing chamber is one of the most challenging components. Oil films on the chamber walls are generated from oil droplets, ligaments, or film fragments, which emerge from bearings, seal plates and shafts, and enter the bearing chamber with an angular momentum. Furthermore, shear forces at its surface, gravity forces, and the design of scavenge and vent ports strongly impact the behavior of the liquid film. The present paper focuses on the experimental determination of the film thickness in various geometries of bearing chambers for a wide range of engine relevant conditions. Therefore, each configuration was equipped with five capacitive probes positioned at different circumferential locations. Two analytical approaches are used for a comprehensive discussion of the complex film flow.
5
Назин, Владимир Иосифович. "ВЛИЯНИЕ УГЛОВ ПОЛОЖЕНИЯ КАМЕР НА НАРУЖНЫХ И ВНУТРЕННИХ ЧАСТЯХ ГИДРОСТАТОДИНАМИЧЕСКОГО ПОДШИПНИКА СДВОЕННОГО ТИПА НА ЕГО НЕСУЩУЮ СПОСОБНОСТЬ". Aerospace technic and technology, № 4 (31 серпня 2019): 50–56. http://dx.doi.org/10.32620/aktt.2019.4.09.
Анотація:
The task is to study the bearing capacity of the double type bearing at different angular positions of the chambers on the outer and inner working surfaces. It is given a mathematical model of a double type hydrostatodynamic bearing in a stationary formulation, which makes it possible to determine its bearing capacity. It is considered the cases of laminar and turbulent flow of the working fluid in the slit path of the double type bearing. Both gradient and portable flows of the working fluid are considered in recording the flow of working fluid along the contour of the 1st chamber. The expression for the flow rate of the working fluid at the entrance to the chambers is written for the case of using the jet as a pressure compensator. The cost balance equations and the Reynolds equations, written for both the outer and inner working surfaces of the double type bearing, were solved jointly. Applied assumptions are usually taken in the hydrodynamic theory of lubrication in writing the Reynolds equations. The most common V.N. Constantinescu method was applied for turbulence coefficients. The expression for the balance of expenditure equations and the Reynolds equations are expanded to the dimensionless type. The most effective numerical methods for the numerical implementation of the expenditure balance equations and Reynolds equations are analyzed and applied. The most economical finite-difference method in combination with the longitudinal-transverse sweep method was applied to solve the Reynolds equation. The accuracy of the solution was assigned when determining the pressures in the chambers and on the inter-chamber jumpers. Geometric and operating parameters of the double type bearing were assigned based on currently existing recommendations for the design of fluid-friction bearings. The results of the calculation of the bearing capacity of the double type bearing for different camera angles on the external and internal parts of this bearing are obtained. The results of the calculation of the bearing capacity of the double type bearing in the form of graphs are given. The analysis of the obtained results was made and conclusions were made on the obtained results, allowing designers to more efficiently design bearings of this type.
6
Fang, Long, and Guoding Chen. "The study of droplet deformation and droplet volume fraction in an aero-engine bearing chamber." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 6 (May 24, 2018): 2264–77. http://dx.doi.org/10.1177/0954410018777595.
Анотація:
Inside an aero-engine bearing chamber, the shape, velocity, and temperature of each droplet shed from roller elements keep changing under the actions of the rotating airflow. Research on droplet deformation, droplet motion, and droplet volume fraction is fundamental to the understanding of the complex two-phase flow in an aero-engine bearing chamber. In this paper, the modified Taylor analogy breakup model, equations of temperature and motion are established to obtain the size, temperature, and velocity of a deformed droplet. Subsequently, a method is presented to solve for the droplet volume fraction in a bearing chamber based on the size and motion parameters of deformed droplets. In the end, a simplified bearing chamber experimental setup has been constructed. Comparisons between the experimental results and theoretical calculations show a good match based upon the research analogy used. The research work in this paper can provide theoretical foundations for the analyses of heat exchange and lubrication in bearing chambers. This also has great significance in realizing the rigorous design required for the lubrication system of an aero-engine.
7
Wittig, S., A. Glahn, and J. Himmelsbach. "Influence of High Rotational Speeds on Heat Transfer and Oil Film Thickness in Aero-Engine Bearing Chambers." Journal of Engineering for Gas Turbines and Power 116, no. 2 (April 1, 1994): 395–401. http://dx.doi.org/10.1115/1.2906833.
Анотація:
Increasing the thermal loading of bearing chambers in modern aero-engines requires advanced techniques for the determination of heat transfer characteristics. In the present study, film thickness and heat transfer measurements have been carried out for the complex two-phase oil/air flow in bearing chambers. In order to ensure real engine conditions, a new test facility has been built up, designed for rotational speeds up to n = 16,000 rpm and maximum flow temperatures of Tmax = 473 K. Sealing air and lubrication oil flow can be varied nearly in the whole range of aero-engine applications. Special interest is directed toward the development of an ultrasonic oil film thickness measuring technique, which can be used without any reaction on the flow inside the chamber. The determination of local heat transfer at the bearing chamber housing is based on a well-known temperature gradient method using surface temperature measurements and a finite element code to determine temperature distributions within the bearing chamber housing. The influence of high rotational speed on the local heat transfer and the oil film thickness is discussed.
8
Zhu, Hong Xia, Yingxiao Lin, and Jing Yi Zhao. "Research on the Micro Self-Vibration of Aerostatic Bearing with Pocketed Orifice Type Restrictor." Applied Mechanics and Materials 333-335 (July 2013): 2076–79. http://dx.doi.org/10.4028/www.scientific.net/amm.333-335.2076.
Анотація:
In this paper, Computational Fluid Dynamics (CFD) is used to analyze the micro self-vibration of aerostatic bearing with pocketed orifice type restrictor as the bearings performance is stable and it is widely used ultra-precision equipments. By using Large Eddy Simulation (LES), time-variation flow field inside the bearing is obtained. Then the pressure fluctuation characteristics is discussed because it influences the micro self-vibration of the bearing directly. Moreover, the relationship between bearing diameter, orifice diameter, air chamber diameter, air chamber depth and the micro self-vibration is researched. The results can be considered for the designing of ultra-precision aerostatic bearing with pocketed orifice type restrictor.
9
Nazin, Vladimir. "Identifying the influence of design parameters of a hydrostatic bearing in an aircraft fuel pump on its static characteristics." Eastern-European Journal of Enterprise Technologies 5, no. 1 (125) (October 31, 2023): 28–34. http://dx.doi.org/10.15587/1729-4061.2023.289426.
Анотація:
The object of this study is hydrostatic processes in the sliding bearings of gear-type aviation fuel pumps. The problem of the influence of the design parameters of the fuel pump bearing on its static characteristics was solved. Load-bearing capacity, lubricant consumption, and operating temperature conditions were considered as static characteristics. The determination of these characteristics was based on the pressure distribution function in the working fluid layer. An option was adopted with two load-bearing chambers located on the working surface of the hydrostatic bearing. Three options for the circumferential arrangement of chambers relative to the line of action of the external load were studied. A quantitative assessment of the effect of increasing the temperature of the working fluid on the consumption of lubricant and bearing capacity is given. It has been established that with an increase in the angle of position of chambers relative to the line of action of the external load, the flow rate of the working fluid in the bearing increases, and its load-bearing capacity decreases. With a clearance in the bearing of 0.0225 mm, with an increase in the angle of the chambers from 30° to 40°, the flow of working fluid through the bearing increases by approximately 1.64 times. When the gap increases to 0.0425 mm and the angle of the chambers changes from 30° to 40°, the flow rate of the working fluid increases by approximately 1.2 times. The load-bearing capacity of the bearing with an increase in the chamber position angle from 30° to 40° decreases with a gap of 0.0225 mm by approximately 1.6 times, and with a gap of 0.0425 mm by approximately 1.93 times. An increase in the temperature of the working fluid leads to a decrease in the load-bearing capacity of the bearing by 2.5 % and an increase in the flow rate of the working fluid in the bearing by 4.6 %. The results allow for more rational design of hydrostatic bearings for fuel gear pumps.
10
Yuan, Xi Chuan, Hui Guo, and Liang Yun Wang. "Experiment Study of Heat Transfer in Aeroengine Bearing Chambers." Applied Mechanics and Materials 86 (August 2011): 448–53. http://dx.doi.org/10.4028/www.scientific.net/amm.86.448.
Анотація:
In this paper, a method of heat transfer test research in aeroengine bearing chamber has been introduced. The method attains the law of heat transfer in bearing chamber and the influence of heat transfer coefficient on bearing dn value, oil flow, supply oil temperature, sealing air flow by simulating the oil work condition in turboshaft engine typical high temperature bearing chamber.
Дисертації з теми "Bearing chamber":
1
Lee, Chan Wei. "Air and oil flow investigations in an aeroengine bearing chamber." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408637.
2
Farrall, Mark. "Numerical modelling of two-phase flow in a simplified bearing chamber." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367991.
3
Hehir, Ryan Thomas. "A CFD Investigation of the Two Phase Flow Regimes Inside the Bearing Chamber and De-aerator of a Jet Engine." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/73386.
Анотація:
In a jet engine air and oil are mixed during removal from the bearing chamber. Before the oil can be recycled back into the system it must be separated from the air. This is accomplished through use of a de-aerator and breather. The oil air mixture enters the de-aerator first. The de-aerator is a vertical cylinder in which the air and oil enter from the top of the system. Gravity then pulls the oil down as it circulates along the outer wall of the de-aerator. The air is forced out through a top hole and sent to the breather where any oil droplets which remain are furthered separated. A pedestal is located near the bottom of the de-aerator. The pedestal creates a gap between itself and the de-aerator wall. Ideally this gap should be large enough to allow oil to flow through the gap without pooling on the pedestal, but small enough so that air does not flow through the gap. The oil will pool up on the pedestal and reduce the efficiency of the system. In this research, a 30° conical pedestal with a gap of 10.7% was tested. The results showed that the pedestal gap of 10.7% is too large and allows air to flow through the gap. The maximum water was 8.5% and the average water thickness was 5.11%. After studying both the previous experimental data and current CFD data, it is recommended further testing be conducted on pedestal gaps between 8.5% and 9.5%.Master of Science
4
Miller, Bradley Alan. ""Parable-Art" Beyond the Auden Generation: An Examination of the Message-Bearing Aspects and Architecture of Two Twenty-First-Century Works for Chorus and Chamber Orchestra." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/268472.
Анотація:
English writer and poet Wystan Hugh Auden (1907-1973) introduced the term "parable-art" in his essay "Psychology and Art To-Day" (1935) as a means of describing works of art that are both message-bearing and moralistic in nature. Auden believed that art had the power to influence the affairs of the world, and felt it was the artist's obligation to work for the betterment of society. Though he ultimately rejected this conviction, Auden's influence on his English contemporaries in the 1930s was profound. Perhaps the most notable musician who embraced Auden's ideal was Benjamin Britten (1913-1976), who so often embedded moral, social, and humanitarian themes in his works. Britten was deeply influenced by Auden's philosophical views; therefore, it is logical that the term parable-art has been used to describe many of the composer's works. The expression, however, has never been applied to the works of other composers. I believe that many twentieth- and twenty-first-century works comprise similar parabolic characteristics and can be appropriately labeled parable-art. In this study, I attempt to demonstrate that Stephen Paulus's A Place of Hope (2001) and Ralph M. Johnson's This House of Peace (2008), two choral-orchestral compositions incorporating unconventional, non-literary texts, can be deemed twenty-first-century parable-art. These two compositions were chosen as the focus of this research due to three commonalities: 1) each work was commissioned by an organization dedicated to ethical and humanitarian ideals in healthcare; 2) humanitarian themes, such as gratitude, compassion, kindness, and love, are found in the texts of each composition; 3) each composer incorporated words of patients, family members, visitors, or caregivers at the medical facility for which the respective work was commissioned. Analyses include examinations of each composer's intent, the values of the organizations for which each work was commissioned, and the impact these values had on the selection of texts, the parabolic aspects of the texts, and the compositional techniques employed, which result in textual clarity and effective musical/dramatic affect, thus heightening the communicability of the message.
5
Ishaq, Gazala. "An experimental study of gas/liquid flows in rapidly rotating annular systems." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396133.
6
Maqableh, Ayman M. M. "Computational study of multi-phase air/oil heat transfer in aero-engine bearing chambers." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417410.
7
Peduto, D. "Oil droplet impact dynamics in aero-engine bearing chambers : correlations derived from direct numerical simulations." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28997/.
Анотація:
Bearing Chambers in Aero-Engines are located near the rolling-element type of bearings which support the shafts and accomodate the resulting thrust loads. One of the main task of the bearing chambers is, beside an efficient scavenging of the lubricating oil, the cooling of the hot compartments. A very complex two-phase air-oil flow takes usually place in these bearing chambers consisting of oil droplet-laden air flows and shear-driven liquid wall films. The interaction of the droplets with the wall films is significantly influencing the wall heat transfer and the cooling performance of these systems. For this reason, a detailed characterization and modelling of the mass and momentum exchange between droplets and wall films for the unique impingement parameter range in bearing chambers is inevitable. This scientific report investigates the oil droplet impact dynamics for typical impingement regimes relevant to aero-engine bearing chambers. The application of a Direct Numerical Simulation (DNS) technique based on the Volume-of-Fluid (VOF) method and coupled with a gradient-based adaptive mesh refinement (AMR) technique allowed to characterize the drop impact dynamics during various single micro- and millimeter drop impacts onto thin and thick films. With the help of a special numerical treatment, a self-perturbing mechanism is installed that leads to the correct resolution of the crown disintegration process. The numerical methodology was thoroughly validated using the experimental results of millimeter sized drop impacts onto deep liquid pools. These results were developed with an enhanced back-illuminated high-speed imaging and Particle Tracking Velocimetry (PTV) technique. New insights into the cavity penetration, the crown’s breakup dynamics and the secondary droplet characteristics following a single drop impact have been developed with the help of the isolated variation of different parameters of influence. Particularly the influence of the Froude number, the impingement angle, and the cavity-wall interaction delivered results to date not reported in scientific literature. Beside the advances in fundamental physics describing the drop impact dynamics with the help of the numerical and experimental results, a set of correlations could also be derived. From these correlations, a drop-film interaction model was formulated that is suitable for the parameter range found in bearing chambers.
8
Outirba, Bilal. "Experimental study of the performance and endurance of carbon fiber brush seals for aero-engines bearing chambers." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/258495.
Анотація:
Over the last decades, it has been progressively acknowledged that reducing the specific fuel consumption and the emission of pollutants as well as improving the thrust-to-weight ratio involves extensive research on advanced sealing technologies. Amongst these, brush seals are particularly well considered for their excellent leakage performance, their low friction properties, and their ability to cope with inevitable rotor excursions during flights. This thesis presents the experimental work that has been carried on in order to characterize carbon brush seals performance in function of the bristle pack geometry and the operating conditions. The analyzed parameters are the bristle free length, the density, and the inter-platedistance. The work, performed by the ULB in collaboration with French engine manufacturer Safran Aircraft Engines, provides first, a description of the test installation that reproduces accurately the severe working conditions encountered in a bearing chamber. A total of eight samples were submitted to extensive testing, and allowed to perform a qualitative analysis of the main performance indicators of a brush seal: the leakage flow, and the seal torque. Complex phenomena acting on the bristle pack were put in evidence under the effect of differential pressure androtation speed, and oil, which fundamentally deteriorate the leakage performance of a brush seal. Subsequently, performance models were developed through empirical correlations, based on the experimental data. They predict the leakage flow and the seal torque as a function of the geometrical parameters and operating conditions. In addition, hysteresis issues were also addressed, and an IR camera helped investigating the heat generation properties of a brush seal.Brush seal samples were submitted to endurance testing, in order to highlight wear mechanisms, and study the performance degradation with the operating time. Oil plays a major part in extending brush seals operating life, despite the leakage performance degradation. Finally, the correlations developed throughout the PhD thesis were used to develop an optimization process in function of the operating conditions of a modern aero-engine. Ultimately, large savings in air consumption were put in evidence when replacing labyrinth seals by brush seals.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
9
Kirov, Nikolay. "Simulation numérique de l’écoulement air-huile dans une enceinte moteur." Electronic Thesis or Diss., Toulouse, ISAE, 2024. http://www.theses.fr/2024ESAE0015.
Анотація:
La tendance actuelle vers des moteurs d'avion plus puissants et plus économes en carburant crée le besoin de roulements capables de transférer des charges mécaniques plus élevées entre les composants rotatifs et fixes de la machine, à des températures extrêmes et à des régimes moteur plus élevés. Les roulements nécessitent d'être lubrifié en permanence avec une huile spécialisée afin de réduire les frottements, de dissiper la chaleur, d'éloigner les minuscules débris et ainsi d'assurer l'intégrité mécanique du moteur.Les débits massiques d'huile qui en résultent au sein du moteur sont importants et le lubrifiant doit donc être recyclé en permanence via un système de recirculation d'huile. En conséquence, les roulements sont enfermés dans des enceintes, constitués de joints étanchéités et des roulements eux-mêmes. Les enceintes à huile sont essentiellement des chambres étanches adjacentes aux roulements, ou parfois les enfermant, dans lesquelles l'huile éjectée est canalisée après la lubrification. Ils sont généralement scellés avec de l'air sous pression du côté opposé, qui passe à travers un joint labyrinthe afin d'empêcher tout écoulement sortant. En règle générale, une ouverture d'orifice de ventilation est incluse sur le dessus pour permettre à l'air de s'échapper, et une ouverture d'orifice de récupération est située près du bas pour ramener l'huile vers les pompes de récupération d'huile vers le réservoir.À l'intérieur de l'enceinte, l'huile et l'air forment un écoulement complexe à deux phases, dans lequel les effets centrifuges, le cisaillement aérodynamique et les forces de gravité provoquent la dispersion de la majorité de l'huile dans l' enceinte huile et s'accumulent sous forme de film dans les parois extérieures. Un transfert de chaleur de ces parois vers l'huile pré-refroidie à lieu, lui conférant ainsi une fonction secondaire importante : absorber une partie de la chaleur et donc refroidir l'enceinte. Il est cependant important que l'huile des roulements soit collectée et renvoyée au réservoir avant d'atteindre des températures trop élevées, afin d'éviter la cokéfaction ou, pire encore, l'inflammation, qui pourrait déclencher un incendie dans l'enceinte. La physique complexe des écoulements diphasiques conduit à un problème d'optimisation qui ne peut être résolu que via des simulations numériques.À ce jour, une quantité considérable d’incertitude demeure quant à la pratique de modélisation informatique la plus optimale pour une simulation précise, fiable et rentable des chambres de roulements dans différentes conditions de fonctionnement. L'objectif de cette thèse est donc de tester plusieurs approches de modélisation numérique pour la simulation d'un banc d'essai simplifié de enceinte, ici nommé ELUBSYS, pour lequel certaines mesures expérimentales sont disponibles et peuvent être utilisées pour fournir des moyens de validation desdites approches. Il s’agit, à savoir, d’une approche interfaciale multi-fluide à interface diffuse, d’une approche simplifiée Eulerian Integral Thin Film (EITF), d’une approche à phase dispersée Lagrangienne (Disperse Particles Model, DPM) et, enfin, d’une approche couplée EITF-DPM. Au cours de toutes ces investigations, de nouvelles connaissances ont été acquises sur les caractéristiques de l'écoulement, les paramètres d'influence et les performances globales, par rapport aux données expérimentales pour deux configurations de chambres de roulements sous une variété de débits massiques d'huile et de vitesses de rotation de l'arbre.La méthodologie couplée EITF-DPM s'est avérée obtenir une bonne précision pour les mesures de distribution d'épaisseur de film pour un coût contenu et pour une variété de régimes de fonctionnementThe current trend towards more powerful and fuel-efficient aircraft engines produces the need for bearings, capable of transferring higher mechanical loads between rotating and stationary machine components, at extreme temperatures and higher engine speeds. The bearings demand lubrication oil at all times in order to reduce friction, dissipate heat, drive tiny debris away and therefore ensure the mechanical integrity of the engine.The resulting oil mass flow rates within the engine are significant and thus the lubricant must be continuously recycled via an oil recirculation system. As a result, the bearings are encompassed within oil sumps, consisting of chambers, seals and the bearings themselves. The bearing chambers are essentially sealed chambers adjacent to, or sometimes enclosing the bearings, whereby the ejected oil is channeled into after lubrication. They are typically sealed with pressurised air on the opposite side, which is passed through a labyrinth seal in order to provide flow obstruction. Typically, a vent port opening is included on the top for the air to escape, and a scavenge port opening is located near the bottom to lead the oil to the oil scavenge pumps back to the reservoir.While still contained within the bearing chamber, the oil and the air form a complex two-phase flow, whereby centrifugal effects, aerodynamic shear and gravity forces cause the majority of the oil to disperse within the bearing chamber and accumulate as film on its outer stationary walls. Heat transfer from these walls to the pre-cooled oil takes place, therefore giving it an important secondary function - to absorb some of the heat and therefore cool the bearing chamber enclosure. It is important, however, that the oil from the bearings is collected and returned to the reservoir before reaching temperatures that are too high, in order to avoid coking or even worse - ignition, that can start a fire within the bearing chamber. The complex two-phase flow physics lead to an optimisation problem which can only be tackled via numerical simulations.To date, a considerable amount of uncertainty remains concerning the most optimal computational modelling practice for the accurate, reliable and cost-efficient simulation of bearing chambers across different operating conditions. The objective of this thesis, is therefore to test several computational modelling approaches for the simulation of a simplified bearing chamber test rig, hereby named ELUBSYS, for which some experimental measurements are available that can be used to provide means of validation of the said approaches. These are, namely, an interfacial multi-fluid diffuse-interface approach, an Eulerian Integral Thin Film (EITF) approach, a two-way coupled Discrete Parcel Method approach, and, lastly, an EITF-DPM coupled approach. During all of these investigations, new knowledge has been gained for the flow field characteristics, influencing parameters and overall predictory performance, as compared to the experimental data for two bearing chamber configurations under a variety of oil mass flow rates and shaft rotational speeds.The cost-efficient coupled EITF-DPM methodology proposed within this thesis was found to obtain good accuracy for the film thickness distribution measurements for a variety of operating conditions
10
Peduto, Davide [Verfasser], H. J. [Akademischer Betreuer] Bauer, and D. [Akademischer Betreuer] Hann. "Oil Droplet Impact Dynamics in Aero-Engine Bearing Chambers - Correlations derived from Direct Numerical Simulations / Davide Peduto. Betreuer: H.-J. Bauer ; D. Hann." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1072464527/34.
Книги з теми "Bearing chamber":
1
Mordaunt, John. The proceedings of a general court-martial held in the Council-Chamber at Whitehall, on Wednesday the 14th, and continued by several adjournments to Tuesday the 20th of December 1757, upon the trial of Lieutenant-General Sir John Mordaunt, by virtue of His Majesty's warrant, bearing date the 3d day of the same month. London: Printed for A. Millar ..., 1985.
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Olagunju, M. O. A study of efficient recovery of liquid from fine air-liquid mists of the form generated in gas turbine bearing chambers using a rotating porous disc. London: University of East London, 1998.
3
Hinton, Alexander Laban. Subjectivity (DC-Cam and the ECCC Outreach Tour). Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198820949.003.0011.
Анотація:
The chapters in Part III, “Eddies,” seek to step behind this justice facade and explore the lived experience of victim participation as well as the ways in which this experience was mediated by another Cambodian intermediary organization, Documentation Center of Cambodia (DC-Cam). Chapter 7 builds upon the previous chapters by unpacking how the Extraordinary Chambers in the Courts of Cambodia (ECCC) sought to produce a certain liberal democratic, right-bearing juridical subjectivity even as alternative subjectivities also mediated the experience of Cambodians in and around the court. Specifically, Chapter 7 focuses on a non-governmental organization outreach tour, which included attending the first day of two weeks of civil party testimony in which relatives of S-21 victims testified. Three international civil parties—each in many respects exemplary victims embodying the qualities of wound, suffering, helplessness—spoke. Even as they did, it was evident that there were cracks in this justice facade revealing underlying complexities obscured and pushed out of sight. Such fissures were also evident when the outreach participants visited Tuol Sleng and performed a ceremony for the spirits of the dead, highlighting Buddhist subjectivities backgrounded by the juridical process.
Частини книг з теми "Bearing chamber":
1
Wu, Hao Tian, and Guo Ding Chen. "The Calculation of Two-Phase Gas/Liquid Homogenous Flow in Bearing Chambers." In Materials Science Forum, 717–20. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-421-9.717.
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Bremer, Jeroen, and Peter C. van den Akker. "In Vivo Models for the Evaluation of Antisense Oligonucleotides in Skin." In Methods in Molecular Biology, 315–20. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2010-6_21.
Анотація:
AbstractHere, we describe an in vivo model in which antisense oligonucleotides were preclinically evaluated in reconstituted patient and healthy control skin. The aim was to investigate the effect of antisense oligonucleotides upon local or systemic administration. This allows for clinically relevant evaluation of antisense oligonucleotides in an in vivo setting. In this model, primary human keratinocytes and fibroblasts were placed into silicone grafting chambers, implanted onto the back of athymic nude mice. After sufficient cells were expanded, within a few weeks, human skin grafts were generated with a high success rate. These mice bearing grafts were subsequently treated with antisense oligonucleotides targeting exon 105 of the COL7A1 gene which encodes type VII collagen. Patients completely lacking expression of type VII collagen develop severe blistering of skin and mucosa, i.e., recessive dystrophic epidermolysis bullosa. In this chapter, we describe the in vivo model used for the preclinical evaluation of antisense oligonucleotides as therapeutic approach for recessive dystrophic epidermolysis bullosa.
3
Dunne, Fionn, and Nik Petrinic. "Creep in an aero-engine combustor material." In Introduction to Computational Plasticity, 209–18. Oxford University PressOxford, 2005. http://dx.doi.org/10.1093/oso/9780198568261.003.0009.
Анотація:
Abstract Aero-engine components operating under in-service conditions are often subjected to a range of complex cyclic mechanical and thermal loading, leading to combined creep and cyclic plasticity. The polycrystalline nickel-base superalloy (C263) is a commercial alloy used for stationary components in aero-engines such as combustion chambers, casings, liners, exhaust ducting, and bearing housings. It is a fine-precipitate strengthened alloy at 800°C, with a precipitate solvus temperature of 925°C (Betteridge and Heslop, 1974). Combustion chamber applications require the material to undergo temperature fliuctuations between 20°C and 950°C, and the temperature range is therefore such that the precipitate solvus can be exceeded during in-service operation. significant microstructural change is therefore likely to occur during ordinary operation, leading to quite profound changes in the creep mechanisms in the material, controlling both deformation and component life.
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Li, Qi-fei, and Xiao-yan Wang. "Research on the design and performance of face seal in bearing chamber." In Power Engineering, 61–66. CRC Press, 2016. http://dx.doi.org/10.1201/9781315386829-11.
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Omogiade Idahor, Kingsley. "Avian Reproduction." In Veterinary Medicine and Science. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.101185.
Анотація:
There are about 10,400 living avian species belonging to the class Aves, characterized by feathers which no other animal classes possess and are warm-blooded vertebrates with four-chamber heart. They have excellent vision, and their forelimbs are modified into wings for flight or swimming, though not all can fly or swim. They lay hard-shelled eggs which are a secretory product of the reproductive system that vary greatly in colour, shape and size, and the bigger the bird, the bigger the egg. Since domestication, avian species have been basically reared for eggs, meat, pleasure and research. They reproduce sexually with the spermatozoa being homogametic and carry Z-bearing chromosomes, and the blastodisk carries either Z-bearing or W-bearing chromosomes, hence, the female is heterogametic, and thus, determines the sex of the offspring. The paired testes produce spermatozoa, sex hormones and the single ovary (with a few exceptions) produces yolk bearing the blastodisk and sex hormones. Both testis and ovary are the primary sex organs involved in sexual characteristics development in avian. In avian reproduction, there must be mating for fertile egg that must be incubated to produce the young ones. At hatch, hatchling sex is identified and reared to meet the aim of the farmer.
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Leeming, David Adams. "Jesus." In Mythology, 175–78. Oxford University PressNew York, NY, 1998. http://dx.doi.org/10.1093/oso/9780195121537.003.0082.
Анотація:
Abstract And the first day of unleavened bread, when they killed the passover, his disciples said unto him, Where wilt thou that we go and prepare that thou mayest eat the passover? And he sendeth forth two of his disciples, and saith unto them, Go ye into the city, and there shall meet you a man bearing a pitcher of water: follow him. And wheresoever he shall go in, say ye to the goodman of the house, The Master saith, Where is the guest chamber, where I shall eat the passover with my disciples? And he will show you a large upper room furnished and prepared: there make ready for us.
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Der Manuelian, Peter. "The Near-Destruction of Two American Expeditions." In Walking Among Pharaohs, 396—C15.P58. Oxford University PressNew York, 2022. http://dx.doi.org/10.1093/oso/9780197628935.003.0016.
Анотація:
Abstract Clarence Fisher and George Reisner clashed over the treatment of their Egyptian workmen, since all their Qufti families were related. The crisis began with fundamental misunderstandings between Fisher and his Reisner-loaned reis Mahmud el-Meyyit, who turned to Reisner after being fired by Fisher. This threatened the stability of both expeditions, and authorities from both the Penn Museum and the MFA in Boston had to get involved. Ashton Sanborn, working for they paranoid Fisher but bearing no ill will toward Reisner, was caught in the middle. Meanwhile at Nuri, Aspelta’s sixteen-ton sarcophagus was removed from its burial chamber, thanks to Said Ahmed’s ingenuity. Oric Bates died of influenza at Camp Zachary Taylor in 1918 preparing to join the war effort. At last war’s end signaled a return to archaeology for many foreign expeditions.
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Leys, Clyde, Adam Schwarz, Mark Cloos, Sugeng Widodo, J. Richard Kyle, and Julius Sirait. "Chapter 29: Grasberg Copper-Gold-(Molybdenum) Deposit: Product of Two Overlapping Porphyry Systems." In Geology of the World’s Major Gold Deposits and Provinces, 599–620. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.29.
Анотація:
Abstract The supergiant Grasberg porphyry deposit in Papua, Indonesia (5.26 Gt @ 0.61% Cu and 0.57 g/t Au, with no cutoff applied) is hosted by the Grasberg Igneous Complex that fills an upward-flared diatreme ~1,800 m wide at the 4,250-m surface elevation. The Grasberg Igneous Complex is emplaced into folded and strike-slip faulted Tertiary and older sediments and comprises 3.6 to 3.3 Ma Dalam monzodiorite intrusions and subordinate volcanic rocks occupying much of the pipe, the central 3.2 Ma Main Grasberg intrusion, and the NW-SE-trending 3.2 to 3.0 Ma Kali dikes. The Grasberg Igneous Complex contains two porphyry systems: Gajah Tidur copper-(molybdenum) and Main Grasberg copper-gold. The Gajah Tidur intrusion belongs to the Dalam igneous group and is a 3.4 Ma porphyritic monzonite with its top at a 2,750-m elevation; it is overprinted by an extensive, domal, quartz stockwork, with a low-grade and intensely phyllic-altered core, surrounded by molybdenite-bearing veins, with a pre-Main Grasberg Re-Os age, as well as chalcopyrite and overprinting pyrite-covellite veins. The strongly potassic-altered, Main Grasberg monzodiorite porphyry extends from surface to the 2,700-m elevation and is overprinted by a cylindrical, ~1-km-diameter, intense quartz-magnetite stockwork cut by abundant chalcopyrite-bornite veins with rare molybdenite dated at 3.09 Ma. A 700-m-wide annulus of chalcopyrite overprinted by pyrite-covellite-mineralized phyllic alteration surrounds the stockwork. Altered and mineralized Main Grasberg and surrounding Dalam rocks were subsequently wedged apart by the largely unmineralized Kali dikes. Gold is predominantly associated with the Main Grasberg porphyry system where it occurs as 1- to 150-µm (avg ~15 µm) native gold inclusions within chalcopyrite and bornite. Melt and fluid inclusions from Main Grasberg stockwork quartz veins, which exhibit crack-seal textures, comprise K-feldspar-rich silicate melt, sulfide melt, virtually water-free salt melt, and coexisting hypersaline and vapor-rich fluids. Factors important in forming the Grasberg deposit include the following: (1) generation of highly oxidized fertile magma in a postsubduction tectonic setting; (2) efficient extraction of metals from the parental magma chamber; (3) prolonged maintenance of a fluid-accumulating cupola in a strike-slip structural setting that delivered multiple overlapping discharges of metal-rich fluid; (4) highly focused fluid flow into a narrow, permeable stockwork zone in which a steep temperature gradient enabled highly efficient copper and gold precipitation and led to high ore grades; (5) limited dilution by postmineral intrusions; (6) the youthfulness of the deposit minimized erosion and resulted in preservation of nearly all the high-grade Main Grasberg porphyry orebody; and (7) the proximity of the two porphyry centers enables them to be mined as a single, large deposit. The Gajah Tidur copper-(molybdenum) and Main Grasberg copper-gold porphyry centers overlap in space and formed within ~250,000 years of one another. However, their distinct metal endowment, depth of emplacement, and geometry indicate that they formed under different magmatic, hydrothermal, and structural conditions, which are the subject of ongoing research.
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Ryland, J. S. "Bryozoans." In Handbook of the Marine Fauna of North-West Europe, 629–61. Oxford University PressOxford, 1995. http://dx.doi.org/10.1093/oso/9780198540540.003.0011.
Анотація:
Abstract Bryozoans (Phylum Bryozoa) are sessile, colony-forming coelomates. Each colony arises by asexual budding from an ancestrula formed by the metamorphosis of a sexually produced larva. The individual units of the colony, or zooids, remain in communication with each other through pores. Zooid polymorphism is developed to a varying degree: the normal feeding zooids are termed autozooids and specialized morphs are called heterozooids. Each autozooid has a circular lophophore bearing a series of slender, ciliated tentacles, which can be withdrawn into an anterior introvert of the body, called the tentacle sheath. The alimentary canal is deeply looped, so that the anus opens near the mouth, but just outside the lophophore. The skeletal component of the zooid is sometimes termed the zooecium, in contrast to the viscera which constitute the polypide. Colonies, but not necessarily zooids, are hermaphrodite; embryos are generally brooded, either in the mother zooid or in special brood chambers.
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Xie, Yuling, Philip L. Verplanck, Zengqian Hou, and Richen Zhong. "Chapter 12 Rare Earth Element Deposits in China: A Review and New Understandings." In Mineral Deposits of China, 509–52. Society of Economic Geologists, 2019. http://dx.doi.org/10.5382/sp.22.12.
Анотація:
Abstract China has been the world’s leading rare earth element (REE) and yttrium producer for more than 20 years and hosts a variety of deposit types. Carbonatite-related REE deposits are the most significant REE deposit type, with REY (REE and yttrium)-bearing clay deposits, or ion adsorption-type deposits, being the primary source of the world’s heavy REEs. Other REY resources in China include those hosted in placers, alkaline granites, pegmatites, and hydrothermal veins, as well as in additional deposit types in which REEs may be recovered as by-product commodities. Carbonatite-related REE deposits in China provide nearly all the light REE production in the world. Two giant deposits are currently being mined in China: Bayan Obo and Maoniuping. The carbonatite-related REE deposits in China occur along the margins of Archean-Paleoproterozoic blocks, including the northern, southern, and eastern margins of the North China craton, and the western margin of the Yangtze craton. The carbonatites were emplaced in continental rifts (e.g., Bayan Obo) or translithospheric strike-slip faults (e.g., Maoniuping) along reactivated craton margins. The craton margins provide the first-order control for carbonatite-related REE resources. Four REE metallogenic belts, including the Proterozoic Langshan-Bayan Obo, late Paleozoic-early Mesozoic eastern Qinling-Dabie, late Mesozoic Chishan-Laiwu-Zibo, and Cenozoic Mianning-Dechang belts, occur along cratonic margins. Geologic and geochemical data demonstrate that the carbonatites in these belts originated from mantle sources that had been previously enriched, most likely by recycled marine sediments through subduction zones during the assembly of continental blocks. Although the generation of carbonatite magma is debated, a plausible mechanism is by liquid immiscibility between silicate and carbonate melts. This process would further enrich REEs in the carbonatite end member during the evolution of mantle-derived magma. The emplacement of carbonatite magma in the upper crust, channeled by translithospheric faults in extensional environments, leads to a rapid decompression of the magma and consequently exsolution of a hydrothermal fluid phase. The fluid is characterized by high temperature (600°–850°C), high pressure (up to 350 MPa), and enrichment in sulfate, CO2, K, Na, Ca, Sr, Ba, and REEs. Immiscibility of sulfate melts from the aqueous fluid, and phase separation between CO2 and water may take place upon fluid cooling. Although both sulfate and chloride have been called upon as important ligands in hydrothermal REE transport, results of our studies suggest that sulfate is more important. The exsolution of a sulfate melt from the primary carbonatite fluid would lead to a significant decrease of the sulfate activity in the fluid and trigger REE precipitation. The subsequent unmixing between CO2 and water may also play an important role in REE precipitation. Because of the substantial ability of the primary carbonatite fluid to contain REEs, a large-volume magma chamber or huge fluid flux are not necessary for the formation of a giant REE deposit. A dense carbonatite fluid and rapid evolution hinder long distance fluid transportation and distal mineralization. Thus, carbonatite-related alteration and mineralization occur in or proximal to carbonatite dikes and sills, and this is observed in all carbonatite-related REE deposits in China. Ion adsorption-type REE deposits are primarily located in the South China block and are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits. Hydrothermal alteration by fluids exsolved from late Mesozoic granites or related alkaline rocks (e.g., syenite) may have enriched the parent rocks in REEs, particularly the heavy REEs. Furthermore, this alteration process led to the transformation of some primary REE minerals to secondary REE minerals that are more readily broken down during subsequent weathering. During the weathering process, the REEs are released from parent rocks and adsorbed onto kaolinite and halloysite in the weathering profile, and further enriched by the loss of other material to form the ion adsorption-type REE deposits. A warm and humid climate and a low-relief landscape are important characteristics for development of ion adsorption REE deposits.
Тези доповідей конференцій з теми "Bearing chamber":
1
Chandra, Budi, Kathy Simmons, Stephen Pickering, and Marc Tittel. "Factors Affecting Oil Removal From an Aeroengine Bearing Chamber." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22631.
Анотація:
Aeroengines incorporate various bearing chambers that house the shaft bearings and the oil used to cool and lubricate these bearings must subsequently be recovered from these chambers. Effective oil removal (scavenge) is essential to avoid heat generation through unnecessary working of the oil which can lead to excessive heat generation and reduced overall efficiency. Therefore the design of the scavenge region (sump) in a bearing chamber, as well as the ability to assess its performance is very important. An ongoing research program into bearing chamber scavenge comprising experimental and computational components is being conducted at the University of Nottingham Technology Centre in Gas Turbine Transmission Systems. This program is enhancing understanding of sump performance and design. In this paper an experimental study into a simplified but representative scavenge is reported. This experimental work helps to further understanding of the complex two-phase flow physics in a bearing chamber, particularly in the scavenge region, by means of various measurements and flow visualization. For the study a bespoke test rig has been built. It consists of a simplified, generic bearing chamber with simple sump geometry constructed entirely of Perspex to allow visualization. A shaft in the centre of the chamber capable of rotating up to 15,000 rpm is employed to introduce a windage flow in the chamber. Water (the working fluid) is fed to the chamber via an inlet pump and an outlet pump removes liquid from the chamber, closing the circuit. Several pneumatic pinch valves are installed in the flow circuit to allow residence volume measurement. A completely air-tight reservoir with internal baffle functions as a simple liquid-gas separator, allowing measurement of gas volumetric flow rate in the off-take pipe; hence the scavenge ratio (ratio of total exit volume to liquid volume) can be obtained. Residence volume measurements highlight the importance of sump geometry as an ill-designed sump can lead to an undesirable increase in residence volume.
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von Plehwe, Felix C., Benedikt Brox, Corina Schwitzke, and Hans-Jörg Bauer. "Experimental Investigation of the Influence of Chamber Geometry on Bearing Chamber Oil Leakage." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63561.
Анотація:
This paper presents experimental results identifying the influence of chamber geometry on the oil leakage behaviour of an aero engine bearing chamber. The varied geometrical parameters were the size of the bearing chamber, three different drip lip configurations, and a flinger. The position of the flinger was also varied to simulate mechanical and thermal distortions experienced during engine operations. Previous research has shown that the geometry of a bearing chamber influences the complex two phase flow inside it. This flow in turn influences the tendency of a bearing chamber to leak oil under adverse conditions. Since oil leakage from bearing chambers must be avoided for health and safety reasons, this knowledge is of great importance to the designer of a bearing chamber. The influence of the bearing chamber dimensions on oil leakage behaviour through seals has not yet been identified. The results of this work reveal a link between chamber geometry and leakage behaviour. The dependency of oil leakage rates for different chamber dimensions is also influenced by the investigated bearing chamber components. The complex interplay of these influencing factors was investigated and is described in detail.
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Adeniyi, Akinola A., Budi Chandra, and Kathy Simmons. "Computational Study of a Customised Shallow-Sump Aero-Engine Bearing Chamber With Inserts to Improve Oil Residence Volume." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64410.
Анотація:
An aero-engine bearing chamber is a structure that is used to contain and collect oil used in lubricating and cooling the bearings supporting the high-speed engine shafts. There are various bearings in an aero-engine. Within the bearing chambers, there are typically the bearings, rotating shafts, seals and gears (in some designs). The walls of the bearing chamber are stationary and there are vents and sumps to take out the oil, via an offtake pipe, and the sealing air. The oil collected via the sump and vents is recycled and used again in the loop. To prevent oil degradation and reduce chance of coking in the chamber, it is desired that all of the oil goes through the recycling loop, with no oil staying longer than necessary in the chamber. The sealing air is used to maintain a positive pressure to keep the oil within the chamber. The flow inside a bearing chamber is highly turbulent and consists of a rotating mixture of oil and air. A smaller amount of the oil, mostly as oil-droplets, exits at the vents and is separated from the air using de-aerators [1]. It is expected that by gravity, most of the oil collects at the sump and can be easily scavenged. This is provided the sump can be large enough. The geometry of a bearing chamber is, however, complex largely because of space limitations. It is very important that oil is not resident longer than necessary to prevent over-heating and therefore deterioration or coking. Experimental observations by Chandra & Simmons [2], have shown that bearing chambers with deep sumps perform better that those with shallow sumps. Since shallow sumps are inevitable, a number of innovative studies have been done to improve bearing chamber designs. The presence of air in the oil (e.g. as bubbles) reduces the efficiency of the scavenging pump. Other factors such as oil momentum and windage can take oil away from the off-take pipe potentially increasing oil residence volume. Chandra & Simmons [2] placed inserts such as grille cover, perforated plate, etc, on a side of the bearing wall and improvements in the residence volume were seen. In this work, we are looking at a detailed computational fluid dynamics (CFD) simulation of one of the inserts that performed well. This will aid understanding of the flow characteristics of using an insert to improve oil residence in a bearing chamber.
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Adeniyi, Akinola A., Hervé P. Morvan, and Kathy A. Simmons. "A Multiphase Computational Study of Oil-Air Flow Within the Bearing Sector of Aeroengines." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43496.
Анотація:
The bearing chamber of an aeroengine houses roller bearings and other structural parts. The spatial limitation, high operational speeds of the HP shaft and the proximity to the combustion chamber can make the operating conditions of the bearing chamber challenging. A roller bearing consists of an inner race, an outer race and a cage constraining a number of rolling elements. In the aeroengine application, oil is introduced into the bearing chamber via the inner race regions of the bearing into the rolling elements interstices. This provides lubrication for the roller bearings. The source of heat in the bearing chamber is mainly from rolling contact friction and the high temperature of combustion. Cooling results from the oil transport within the bearing chamber and thus an efficient transport of oil is critical to maintaining the integrity of the entire structure. The bearing chamber contains the oil which is eventually scavenged and recycled for recirculation. Experiments have been conducted over the years on bearing chamber flows but often simplified to create the best emulation of the real aeroengine. The complexity of the bearing chamber structure is also challenging for experimental measurements of the oil characteristic in the roller bearing elements and the bearing chamber compartment. Previous experiments have shown that the oil continuum breaks up in the bearing chamber compartment but it is not quantitatively clear how and what parameters affect these. Previous simulation attempt of bearing chamber, also, have been limited by the boundary conditions for the oil. This work presents a computational fluid dynamics (CFD) transient simulation of flow in the bearing sector in an attempt create boundary conditions for such models. The current results show that the oil emerges in the form of droplets into the bearing chamber compartment with speed of the order of 10% of the shaft rotation.
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Eastwick, Carol, Keno Huebner, Barry Azzopardi, Kathy Simmons, Colin Young, and Richard Morrison. "Film Flow Around Bearing Chamber Support Structures." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68905.
Анотація:
Cooling of aero-engine bearing chamber walls is achieved by the through-flow of thin oil films, which are typically only a few millimeters thick. Support structures and other features disrupt both air and oil motion within such chambers, leading to localized variations in the oil film thickness, causing variation in local heat transfer coefficients. An experimental study has been undertaken to establish the range of conditions under which dry-out occurs upstream and downstream of an obstruction. In addition film thickness measurements around the obstruction have been taken at a set air flow rate for four different liquid flow rates. A regime map of liquid vs. air Reynolds numbers has been created showing where stable and fluctuating type I and II dry-outs occur.
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Gorse, P., S. Busam, and K. Dullenkopf. "Influence of Operating Condition and Geometry on the Oil Film Thickness in Aero-Engine Bearing Chambers." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53708.
Анотація:
Increasing the efficiency of modern jet engines do not only imply to the mainstream but also to the secondary air and oil system. Within the oil system the bearing chamber is one of the most challenging component. Oil films on the chamber walls are generated from oil droplets, ligaments, or film fragments, which emerge from bearings, seal plates and shafts, and enter the bearing chamber with an angular momentum. Furthermore, shear forces at its surface, gravity forces, and the design of scavenge and vent ports strongly impact the behavior of the liquid film. The present paper focuses on the experimental determination of the film thickness is various geometries of bearing chambers for a wide range of engine relevant conditions. Therefore, each configuration was equipped with five capacitive probes positioned at different circumferential locations. Two analytical approaches are used for a comprehensive discussion of the complex film flow.
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Gorse, Ph, K. Willenborg, S. Busam, J. Ebner, K. Dullenkopf, and S. Wittig. "3D-LDA Measurements in an Aero-Engine Bearing Chamber." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38376.
Анотація:
For future efficient and light aero-engines it is essential to develop optimized lubrication systems. These systems require increased temperature and pressure levels in combination with high rotational speeds without compromising the high level of safety and reliability. This applies especially to the bearing chamber as one of the most challenging components of the oil system. Due to the mixing of the sealing airflow and the lubrication oil a complex air- / oilflow is formed inside the chamber. In order to gain a deeper insight into the physical phenomena of the flow inside the bearing chamber a multiyear fundamental study has been initiated. This study focuses for the first time on detailed measurements of the local air- / oilflow field. In the first phase of the project experiments have been carried out to determine the rotating and swirling pure airflow. Hence a specially adapted three dimensional Laser Doppler Anemometry (LDA) system was used to resolve the complex flow. The results revealed that different flow patterns occurred depending on the ratio between the shaft speed and the airflow rate. In the near future it is aimed to resolve the droplet flow also to provide a complete knowledge of the air- / oilflow in bearing chambers.
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Chandra, Budi, Kathy Simmons, Stephen Pickering, Steven H. Collicott, and Nikolas Wiedemann. "Study of Gas/Liquid Behaviour Within an Aeroengine Bearing Chamber." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68753.
Анотація:
Aeroengine bearing chambers typically contain bearings, seals, shafts and static parts. Oil is introduced for lubrication and cooling and this creates a two phase flow environment that may contain droplets, mist, film, ligaments, froth or foam and liquid pools. Some regions of the chamber contain a highly rotating air flow such that there are zones where the flow is gravity dominated and zones where it is rotation dominated. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems, is conducting an ongoing experimental program investigating liquid and gas flow behavior in a relevant highly rotating environment. Previously reported work by Chandra et al [1, 2] has investigated film thickness and residence volume within a simplified chamber consisting of outer cylindrical chamber, inner rotating shaft and cuboid off-take geometry (termed the generic deep sump). Recently a more aeroengine relevant bearing chamber offtake geometry has been studied. This geometry is similar to one investigated by Chandra [3] at Purdue University and consists of a “sub-sump” region approached by curved surfaces linked to the bearing chamber. The test chamber consists of an outer, stationary cylinder with an inner rotating shaft. The rig runs at ambient pressure and the working fluid (water) is introduced either via a film generator on the chamber wall or through holes in the shaft. In addition to visual data (high speed and normal video), liquid residence volume within the chamber and film thickness were the two numerical comparators chosen. Data was obtained for a number of liquid supply rates, scavenge ratios and shaft rotation speeds. The data from the current model is compared to that from the earlier studies [1, 2, & 3]. The data shows that in contrast to the previously reported generic deep sump study, the residence volume of the curved wall deep sump (CWDS) designs is far less sensitive to shaft speed, liquid supply rate and scavenge ratio. The method of liquid supply only makes a significant difference at the lowest scavenge ratios. Residence volume data for the Nottingham CWDS is comparable, when appropriately scaled, to that for the Purdue design. The film thickness data shows that at the lower shaft speeds investigated the flow is gravity dominated whereas at higher shaft speeds shear dominates.
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Tatar, Volkan, and Altug Piskin. "Numerical Investigation on Bearing Chamber Wall Heat Transfer." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75721.
Анотація:
Bearing chamber of a gas turbine engine is generally sealed by pressurized air, separating lubricant from the other zones of the engine. Heat transfer from the wall to air/oil mixture is a challenging engineering problem; predicting heat transfer rate from bearing chamber to oil is important to avoid oil coking and oil fires under high rotational speeds, pressure levels and turbine inlet temperatures. In this study, the inner wall temperature of bearing chamber which is located at the center of front engine structure was investigated numerically. The numerical study involved mainly two thermal modelling methods having two different empirical correlations was performed with finite element solver in order to calculate heat transfer on the wall. First method was based on rotational Reynolds number and Prantl number, in addition to these numbers second one, which is suggested in the literature, is based on oil related and sealing air related Reynolds number, mixture temperature and mixture mass flow. Second approach considers existence of a mixing of gaseous and liquid flow in the core flow unlike first modelling approach. The thermal model was solved by finite element solver and numerical model, assumptions were described with thermal boundary conditions. On the other hand, wall and air thermocouple readings were taken through engine test from the bearing chamber for real engine operating conditions having mainly idle, cruise and maximum power. DN number ranges from 712564 to 2742404, sealing air flow ranges from 46 to 78 g/s and oil flow ranges 22 to 40 g/s for these conditions. The calculated heat transfer coefficients were presented and discussed. The wall temperature predictions of the thermal models, and test measurements were compared. The comparison revealed that analysis results obtained with both correlations were in reasonable agreement with the test. In overall, the second approach predicted metal temperature slightly better at the front support and inner manifold wall, while first approach predicted much better at the rear support wall.
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Chandra, Budi, and Kathy Simmons. "Transient Two-Phase Effects in an Aeroengine Bearing Chamber Scavenge Test Rig." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37554.
Анотація:
Aeroengine bearing chambers typically contain bearings, seals, shafts and static parts. Oil is introduced for lubrication and cooling and this creates a two phase flow environment that may contain droplets, mist, film, ligaments, froth or foam and liquid pools. Efficient and effective liquid removal from a bearing chamber is a functional requirement and in recent years the University of Nottingham Technology Centre in Gas Turbine Transmission Systems has been conducting an experimental and computational research program one strand of which is investigating bearing chamber off-take flows. Initial investigations focussed on a chamber where there was a relatively deep pocket for oil collection below the chamber [1, 2]. In more recent studies Chandra et al have investigated a shallower geometry [3]. In both sets of studies, chamber residence volume and wall film thickness data have been obtained for a range of shaft speeds, scavenge ratios and liquid supply rates. Two methods of introducing liquid to the chamber have been used: a film generator that puts liquid directly onto the chamber wall and a droplet inlet system that distributes droplets from the rotating shaft. During some of the previous investigations, visual data relating to the two phase flow in the outlet pipe immediately below the chamber was gathered together with data from pressure transducers one located in this pipe and one on the chamber itself. It has been observed that for some parameter combinations the chamber flow is gravity dominated whereas for others (typically at higher shaft speeds) the flow is shear dominated. During transition between regimes a pressure spike on the pipe pressure transducer is observed and this may be linked to a change in two phase flow regime within the outlet pipe. A study by Baker et al [4] on transient effects in gas-liquid separation has shown pressure spikes during transitions to new equilibrium conditions for two-phase pipe flow where the gas flow rate is suddenly increased. In this paper outlet visualisation, chamber visualisation and pressure data are combined and conclusions are drawn relating to the parameters controlling whether shear or gravity dominate. The effect of the chamber flow regime on the outlet flow regime is assessed and presented. An implication of the analysis is that during transitional conditions a bearing chamber may contain a different quantity of liquid than in steady state conditions.
Звіти організацій з теми "Bearing chamber":
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Hefetz, Abraham, and Justin O. Schmidt. Use of Bee-Borne Attractants for Pollination of Nonrewarding Flowers: Model System of Male-Sterile Tomato Flowers. United States Department of Agriculture, October 2003. http://dx.doi.org/10.32747/2003.7586462.bard.
Анотація:
The use of bee natural product for enhancing pollination is especially valuable in problematic crops that are generally avoided by bees. In the present research we attempted to enhance bee visitation to Male Sterile (M-S) tomato flowers generally used in the production of hybrid seeds. These flowers that lack both pollen and nectar are unattractive to bees that learn rapidly to avoid them. The specific objects were to elucidate the chemical composition of the exocrine products of two bumble bee species the North American Bombus impatiens and the Israeli B. terrestris. Of these, to isolate and identify a bee attractant which when sprayed on M-S tomato flowers will enhance bee visitation, and to provide a procedure of the pheromone application regime. During the research we realized that our knowledge of B. impatiens is too little and we narrowed the objective to learning the basic social behavior of the bees and the pattern of foraging in a flight chamber and how it is affected by biogenic amines. Colonies of B. impatiens are characterized by a high number of workers and a relatively small number of queens. Size differences between queens and workers are pronounced and the queen seems to have full control over egg laying. Only about 9% of the workers in mature colonies had mature oocytes, and there were no signs of a "competition phase" as we know in B. terrestris. Queens and workers differ in their exocrine bouquet. Queen's Dufour's gland possesses a series of linear, saturated and unsaturated hydrocarbons whereas that of workers contains in addition a series of wax-type esters. Bees were trained to either visit or avoid artificially scented electronic flowers in a flight chamber. Since bee also learned to avoid scented non-rewarding flowers we attempted to interfere with this learning. We tested the effect of octopamine, a biogenic amine affecting bee behavior, on the choice behavior of free-flying bumblebees. Our results show that octopamine had no significant effect on the bees' equilibrium choice or on the overall rate of the behavioral change in response to the change in reward. Rather, octopamine significantly affected the time interval between the change in reward status and the initiation of behavioral change in the bee. In B. terrestris we studied the foraging pattern of the bees on tomato flowers in a semi commercial greenhouse in Yad Mordechai. Bee learned very quickly to avoid the non- rewarding M-S flowers, irrespective of their arrangement in the plot, i.e., their mixing with normal, pollen bearing flowers. However, bees seem to "forget" this information during the night since the foraging pattern repeats itself the next morning. Several exocrine products were tested as visitation enhancers. Among these, tarsal gland extracts are the most attractive. The compounds identified in the tarsal gland extract are mostly linear saturated hydrocarbons with small amounts of unsaturated ones. Application was performed every second day on leaves in selected inflorescences. Bee visitation increased significantly in the treated inflorescences as compared to the control, solvent treated. Treatment of the anthers cone was more effective than on the flower petals or the surrounding leaves. Methanol proved to be a non-flower-destructive solvent. We have shown that bumble bees (B. terrestris) can be manipulated by bee-borne attractants to visit non-rewarding flowers. We have further demonstrated that the bees learning ability can be manipulated by applying exogenously octopamine. Both methods can be additively applied in enhancing pollination of desired crops. Such manipulation will be especially useful in tomato cultivation for hybrid seed production.