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Articles de revues sur le sujet "Oil-jet Losses"
1
Fondelli, Tommaso, Antonio Andreini, Riccardo Da Soghe, Bruno Facchini et Lorenzo Cipolla. « Numerical Simulation of Oil Jet Lubrication for High Speed Gears ». International Journal of Aerospace Engineering 2015 (2015) : 1–13. http://dx.doi.org/10.1155/2015/752457.
Texte intégralRésumé :
The Geared Turbofan technology is one of the most promising engine configurations to significantly reduce the specific fuel consumption. In this architecture, a power epicyclical gearbox is interposed between the fan and the low pressure spool. Thanks to the gearbox, fan and low pressure spool can turn at different speed, leading to higher engine bypass ratio. Therefore the gearbox efficiency becomes a key parameter for such technology. Further improvement of efficiency can be achieved developing a physical understanding of fluid dynamic losses within the transmission system. These losses are mainly related to viscous effects and they are directly connected to the lubrication method. In this work, the oil injection losses have been studied by means of CFD simulations. A numerical study of a single oil jet impinging on a single high speed gear has been carried out using the VOF method. The aim of this analysis is to evaluate the resistant torque due to the oil jet lubrication, correlating the torque data with the oil-gear interaction phases. URANS calculations have been performed using an adaptive meshing approach, as a way of significantly reducing the simulation costs. A global sensitivity analysis of adopted models has been carried out and a numerical setup has been defined.
2
Wang, Lin, Ze-kai Du, Yong Wang, Zhi-zhen Zheng et Guo-ding Chen. « Temperature measurement and error analysis of the transverse plane of oil-jet-lubrication herringbone gear with infrared pyrometers ». Review of Scientific Instruments 94, no 2 (1 février 2023) : 024902. http://dx.doi.org/10.1063/5.0098729.
Texte intégralRésumé :
Frictional power losses of high-speed and heavy-load herringbone gearboxes increase the temperature of the gearbox. Thus, real-time surface temperature measurement is significant for evaluating the gearbox lubrication design. A rotating gear test rig with an infrared pyrometer is developed in this paper to conduct real-time and accurate temperature measurements of the transverse plane of the oil-jet-lubrication herringbone gear. First, the influencing factors and measuring errors of surface temperature are analyzed using the infrared pyrometer. The emissivity of the measured surface of a gear tooth painted with matte black is experimentally calibrated. Second, the temperature measurement tests of the oil-jet-lubrication herringbone gear under different conditions are carried out. Measurement errors resulting from purge air pressure, purge air temperature, and oil-jet temperature are also experimentally studied. The results indicate that the purge gas flow can reduce the measurement errors of the infrared pyrometer resulting from oil mist with an appropriate purge air pressure and purge air temperature. Finally, a mathematical curve-fitting of the measurement results between the infrared pyrometer and thermocouple is carried out. The calculated temperatures by the curve-fitting formula are compared with the measured thermocouple temperature, with the relative differences being less than 1 °C. Thus, the curve-fitting formula is credible for the real-time measurement of surface temperature, while the relevant measuring method is also valuable for engineering applications of high-speed gear systems under oil-jet-lubrication conditions.
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Panevnyk, D. A. « Improving the Energy Efficiency of the Use of Oil Jet Pumps ». ENERGETIKA. Proceedings of CIS higher education institutions and power engineering associations 65, no 2 (5 avril 2022) : 181–92. http://dx.doi.org/10.21122/1029-7448-2022-65-2-181-192.
Texte intégralRésumé :
The substantiation of the choice of design parameters characterizing the mutual orientation of the mixed flows and the ratio of the geometric dimensions of the elements of the flow path of the jet pump that provide an increase in the energy characteristics of borehole ejection systems is given. Depending on the mutual orientation of the mixed flows, three variants of the design of the jet pump are possible, viz. the one with a parallel orientation of the working and ejected flows, the one with the inlet of the ejected flow at a sharp angle, and the one with a perpendicular orientation of the working and ejected flows. The magnitude of the angle between the velocity vectors of the mixed flows directly affects the intensity of vortex formation in the mixing chamber, the amount of energy loss and the efficiency of the jet pump; however, the simplicity of their manufacture remains the determining condition for choosing the design variant of the elements of ejection systems. Based on the use of the laws of conservation of energy, the amount of motion and continuity of the flow, it is determined that the level of energy loss during mixing flows is directly proportional to the magnitude of the angle of entry of the ejected medium. In the course of computer simulation of the jet pump workflow, an asymmetric distribution of hydrodynamic parameters for the non-parallel orientation of the mixed flows has been obtained. In order to reduce energy losses when mixing flows, the value of the angle of entry of the ejected flow must be taken in the range from 0 to 15°. In the case of the implementation of the zero head mode and the maximum ejection coefficient, minimal energy losses during mixing of flows are provided for the main geometric parameter of the jet pump equal to 2.375. In the course of experimental studies, the inverse dependence of the maximum value of the efficiency of a borehole jet pump on the value of its main geometric parameter represented as a power function, has been established. When using ejection systems that implement long-term technological processes (e. g., during oil production), it is necessary to take the minimum possible value of the main geometric parameter of the jet pump for the specified operating conditions.
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Panevnyk, D. O. « Investigation of the flow twist influence on the well jet pumps characteristic ». Prospecting and Development of Oil and Gas Fields, no 4(77) (28 décembre 2020) : 31–40. http://dx.doi.org/10.31471/1993-9973-2020-4(77)-31-40.
Texte intégralRésumé :
The scope of downhole ejection systems is limited by the low value of the efficiency of the jet pump, the value of which usually does not exceed 35 %. Significant energy losses when mixing flows are the reason for the low efficiency of the jet pump. The energy performance of the downhole ejection system can be increased by creating swirling vortex circulating currents in the flow part of the jet pump. This optimizes the nature of the flow mixing and increases the energy performance of the jet pump. In the process of studying the structures, features of the working process and usage experience of ejection systems designed for drilling, operation and repair of oil and gas wells, it is established that the twisting of the working medium in downhole jet pumps can be carried out using guide elements placed at a certain angle in the oncoming flow and rotation of individual parts of the ejection system by means of an external drive and hydraulic turbines. The use of guide elements and hydraulic turbines necessitates the use of part of the energy of the working flow, which drives the downhole jet pump, to spin the working medium. In oil and gas ejection systems, the twisting of working, injected and mixed streams can be realized, as well as the combined simultaneous twisting of several streams. In the process of analyzing the experience of using vortex jet devices, it has been found that the flow twist allows to increase the injection coefficient of the jet pump by 38.1 %, efficiency – up to 70 %, vacuum in the receiving ch amber – up to 40 %. The increase in the basic geometric pa-rameter of the jet pump reduces the effect of flow twist on the characteristics of the ejection system. Flow twisting in downhole jet pumps can be recommended in the implementation of long-term processes, for example, in the ex-traction of formation fluid, when the value of the efficiency of the ejection system significantly affects the cost of oil production.
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Pal, Jitendra Singh, Shivalingappa Nagappa Sapali, Anil Tumkur Ramakrishna, Niyaj Dilavar Shikalgar et Ajit Shinde. « Exergy Criteria of Performance of Waste Heat Recovery Applied for Marine Auxiliary Boiler ». International Journal of Heat and Technology 40, no 1 (28 février 2022) : 297–303. http://dx.doi.org/10.18280/ijht.400135.
Texte intégralRésumé :
Auxiliary boilers onboard motor ships are the subject of ongoing research. Steam is produced by an auxiliary boiler for fuel heating and cargo oil pumping turbines. This marine boiler is a pressure jet burner water tube auxiliary boiler with a 70-80% efficiency rating. The goal of determining the process and components of irreversibility loss in a system is to identify the process and components of exergy losses. The second law of thermodynamics and the concept of irreversible entropy production are the foundations of this study's exergy technique of analysis. This concept of considering entropy at a given steady-state condition rather than as a change in a process is also one of the features of this exergy analysis of the marine oil-fired boiler. The exergy loss in the combustion chamber was calculated and determined to be 35024 kJ, which is the maximum irreversibility in this maritime auxiliary boiler. A numerical analysis of the current nozzle jet burner is undertaken to evaluate the enhancement of the combustion process. The temperature and velocity contour of the fuel stream passing through the nozzle of this auxiliary boiler's burner depicts atomization.
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Dubei, O. Ya. « The Influence of the Jet Pump Geometry on its Main Technological Parameters ». Prospecting and Development of Oil and Gas Fields, no 4(73) (30 décembre 2019) : 24–34. http://dx.doi.org/10.31471/1993-9973-2019-4(73)-24-34.
Texte intégralRésumé :
In order to test the operational efficiency of jet pumps which are installed at different depths in artificial lift-ed oil wells, it is necessary to establish the relation between their geometry and the maximum achievable operat-ing parameters. For this purpose, a series of experimental laboratory studies is conducted. Their main task is to identify the optimal parameters of a jet pump that works with gas-liquid flows. In the experimental setup, the fluid is supplied by an electric centrifugal pump and the air is injected by a compressor. The setup provides the possibility to regulate the fluid pressure before and after the jet pump, as well as the pressure and gas supply at its inlet. The basic parameters of the setup are calculated according to the criteria of the resemblance to real wells. The influ-ence of the jet pump geometry on its working parameters is estimated by replacing its main elements (nozzle, mix-ing chamber, diffuser). For each of the suggested designs of the jet pump, the pressure and the flow rates in its main cross-sections are measured and their measurement values are compared. On the basis of this comparison the author finds the main regularities for choosing optimal geometry which provides maximum gas offtaking or minimum pressure losses. The basic results of the experimental study are presented in the form of graphical dependencies which allow to make conclusions about the operational efficiency of jet pumps.
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Niel, D., C. Changenet, F. Ville et M. Octrue. « Thermomecanical study of high speed rolling element bearing : A simplified approach ». Proceedings of the Institution of Mechanical Engineers, Part J : Journal of Engineering Tribology 233, no 4 (29 décembre 2017) : 541–52. http://dx.doi.org/10.1177/1350650117750806.
Texte intégralRésumé :
Rolling element bearing is an essential component in mechanical transmission because it reduces friction between two rotating parts. Two main approaches to evaluate power losses are proposed in literature: (i) global engineering models using few input data; (ii) local models which are more accurate but need much more information on rolling element bearing geometry. Based on thermal network approach, an intermediate model is developed in this study. This new model allows obtaining lumped information (temperature of rings) with a minimum of input data (external geometry only) and by using global power loss models. This intermediate model is developed for angular contact ball bearing under oil jet lubrication for high speed application. Thermal network results are compared with experimental findings.
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Lee, Sang Woo, Yong Beom Kim et Joon Sik Lee. « Flow Characteristics and Aerodynamic Losses of Film-Cooling Jets With Compound Angle Orientations ». Journal of Turbomachinery 119, no 2 (1 avril 1997) : 310–19. http://dx.doi.org/10.1115/1.2841114.
Texte intégralRésumé :
Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate the flow characteristics and aerodynamic loss distributions of film-cooling jets with compound angle orientations. For a fixed inclination angle of the injection hole, measurements are performed at various orientation angles to the direction of the mainstream in the case of three velocity ratios of 0.5, 1.0, and 2.0. Flow visualizations for the velocity ratio of 2.0 show that the increase in the orientation angle furnishes better film coverage on the test surface, but gives rise to large flow disturbances in the mainstream. A near-wall flow model has been proposed based on the surface flow visualizations. It has also been found from the flow measurements that as the orientation angle increases, a pair of count-errotating vortices turn to a single strong one, and the aerodynamic loss field is closely related to the secondary flow. Even in the case of the velocity ratio of 2.0, aerodynamic loss is produced within the jet region when the orientation angle is large. Regardless of the velocity ratio, the mass-averaged aerodynamic loss increases with increasing orientation angle, the effect of which on aerodynamic loss is pronounced when the velocity ratio is large.
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Ramanchi, Radhika, Sunita Mehta et Madhavi Vedera. « Equity research and valuation : Jet Airways ». Emerald Emerging Markets Case Studies 7, no 2 (5 juin 2017) : 1–28. http://dx.doi.org/10.1108/eemcs-06-2016-0144.
Texte intégralRésumé :
Subject area This case helps students to analyze non-financial and financial aspects of a company and observe quantitative and qualitative aspects of decisions and decide whether to invest or not and give suggestions to sell, buy or hold stocks. The case is expected to help the students understand and analyze the following points: the overall performance of the company and industry, how fundamental and technical analysis is applied to reach investment decisions, the areas where Jet Airways occupies the top position compared to peer group (competitor analysis), the company’s financial position and valuation with the help of tools and techniques and suggestions and observations to shareholders whether to buy/sell or hold shares. Study level/applicability This case can be used for MBA (Finance) students on equity research and valuation. Students are introduced to the fundamental procedures of equity research and analysis – evaluating sector desirability, financial modeling, equity valuation methods. To enhance research skills, students are required to acquire basic knowledge on macro and micro economic indicators. This case helps students to analyze non financial and financial aspects of a company and observe quantitative and qualitative aspects of decisions and decide whether to invest or not and give suggestions to sell, buy or hold stocks. Case overview Mr Rahul, a consultant in Karvey brokerage house was about to leave the office on the evening of March 24, 2015 when the phone rang. It was Mr Srirag, one of his clients and close friends who was passionate about investing in shares. Mr Rahul with his two decades of experience in monitoring and advising various investment plans has been continuously advising Srirag on different investments in shares. Srirag said “Rahul! You know that I bought many shares in Jet Airways. While studying the annual reports of Jet Airways 2014-2015 about its business profits and losses, I came across a January to March, 2013 business quarter analysis report that wrote about Jet Airways facing a net loss of 4.95 billion rupees due to over debt burden and interest costs. It also stated that the company sold a 24 per cent stake in 2013 to Etihad for 332$ million which is an Abu Dhabi based airline. The news said that the deal would help the company overcome financial challenges, raise cash, cut costs and gain access to the global flight network. I am worried about whether this deal would allow the company to continue its operations from India or not. I am also concerned about the downfall of Kingfisher, a major setback in the aviation industry in India that owes 8,000 crores to its employees, banks, airports, oil companies. I am worried that either my investment in Jet Airways might bring huge losses or the partnership with Etihad airways would result in the reduction of costs and due to joint sales efforts, sharing resources and network integration thereby leading to a valuable share price. Since your guidance has helped in many issues, I would like to know the present condition and future prospectus prevailing in Jet Airways”. With a lot of ambiguity in his mind, he asked Rahul to recommend if he should hold or sell the shares in Jet Airways. Expected learning outcomes The case is expected to help the students understand and analyze the following points: the overall performance of the company and industry, how fundamental and technical analysis is applied to reach investment decisions, the areas where Jet Airways occupies the top position compared to peer group (Competitor analysis), the company’s financial position and valuation with the help of tools and techniques and suggestions and observations to shareholders on whether to buy/sell or hold shares. Supplementary materials The link to the following videos to be sent to participants in advance to help them prepare for the class. www.youtube.com/watch?v=_3XJXTmILyk, Equity Research Presentation: Coca-Cola, www.youtube.com/watch?v=n5pEK_2uItg Write Equity Research Report, format, process, www.youtube.com/watch?v=mMLJccgiSTk Equity Valuation and Analysis-Part I. Subject code CSS 1: Accounting and Finance.
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Stratton, Paul. « Optimising the Model of Gas-Jet Quenching of a Carburised Gear ». Advanced Materials Research 29-30 (novembre 2007) : 37–42. http://dx.doi.org/10.4028/www.scientific.net/amr.29-30.37.
Texte intégralRésumé :
Extensive CFD modelling of cooling using nitrogen jets showed that an array of high velocity gas jets close to its surface could cool the part at a similar speed to oil. The optimum conditions were: an approximately uniform nozzle field with the jets four to eight times their own diameter apart, at a distance from the part to be quenched of a quarter of the diameter of the jets; and a jet velocity of 100 m/s. When these optimised conditions were applied to an idealised gear form, the model suggested that it could be fully hardened if a nitrogen/hydrogen mixture was used. The model was validated by comparison with physical experiments under exactly the same conditions. Unfortunately, although close to the physical results, the model results had some important differences. Part of the difference was explained by the exclusion of radiation losses from the model and part by the use of values for specific heat that were derived from static, rather than dynamic, experiments. When the model was modified to correct these there was closer, but by no means perfect, agreement. The finite element model used at this stage was thought to model the heat transfer accurately, but not the steel. The heat transfer data was therefore applied to a metallurgical model. The results from this model were superior in some respects, particularly regarding the phase changes occurring, although again not perfect, perhaps because of the experimental technique used.
Thèses sur le sujet "Oil-jet Losses"
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FONDELLI, TOMMASO. « Numerical Investigation of Fluid-Dynamic Losses in Power Gearboxes For Aero-Engine Applications ». Doctoral thesis, 2016. http://hdl.handle.net/2158/1064807.
Texte intégralRésumé :
The Geared Turbofan (GTF) technology is one of the most promising engine configurations to sensibly reduce the specific fuel consumption (SFC) by increasing the engine bypass ratio. In this architecture, a power epicyclic gearbox is interposed between the fan and the low-pressure spool, resulting in advantages both at engine and component level.
The SFC is directly affected by the transmission efficiency of the gearbox and indirectly by the weight and the size of the cooling system. Therefore the gearbox performance becomes a key technology to achieve the benefits introduced by the GTF architecture. Although the transmission efficiency is usually higher than 99 %, power losses are important in high power application such as the one under consideration.
A performance enhancement can be achieved developing a physical understanding of the losses within the transmission system. These are classified into load-dependent and load-independent groups. The former are primarily related to a mechanical power loss due to friction at the gear contact, while the latter are related to fluid-dynamic effects. Whilst there has been a large body of work dealing with load-dependent power losses, and suitable models for the prediction are already available, the fluid-dynamic losses still need to be studied and properly modelled.
This research study is aimed at defining CFD methodologies to be used in the comprehension of fluid-dynamic losses in gearbox systems for aero-engine applications, to develop predictive tools to be used in industrial design process. A complete simulation of the multiphase flow within the epicyclic gear train would be too expensive and not useful in the understanding of the various loss mechanisms, so that each one has to be studied individually. Therefore the power losses related to the windage phenomena and to the oil-jet lubrication method were investigated.
The windage losses of a spur gear in free and enclosed configuration have been analysed by means of RANS simulations, defining a reliable numerical setup. The results have been validated by comparison with experimental data. A greater insight into the phenomenon was achieved, which allowed modifying and improving a correlative approach available in literature for calculating the windage power loss, by introducing the effect of the fluid volume enclosed in the gearbox.
Concerning the losses due to the oil-jet lubrication, numerical studies were performed using the Volume of Fluid (VOF) method, within the context of transient RANS calculations. These simulations were aimed at improving the description of the complex physical phenomena characterizing the oil-jet lubrication in high speed gearing systems. However VOF approach requires a very fine mesh in the liquid region, leading to considerable computational efforts. In this respect, a strategy for automatic grid adaptation was developed, reducing heavily the numerical effort. VOF simulations were performed varying the oil injection angle and the injection velocity, to assess how these parameters affect the power losses as well as the lubrication performance. As main results, a simplified formulation for the prediction of the power losses due to the oil-jet lubrication has been developed, and then an optimum configuration for such a system was defined. The presented VOF study is one of the first in literature which provides detailed insight on the physic of the oil-jet lubrication.
Finally, the methodologies developed in this work have been partially validated by comparisons with preliminary experimental measurements performed on the High-Speed Test Rig, set up at the University of Florence, which was designed with input from the present research work.
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MASSINI, DANIELE. « EXPERIMENTAL INVESTIGATION ON THE FLUID-DYNAMIC LOSSES IN POWER GEARBOXES FOR AEROENGINE APPLICATIONS ». Doctoral thesis, 2017. http://hdl.handle.net/2158/1085153.
Texte intégralRésumé :
Enhancing the efficiency of gearing systems is an important topic for the development of future aero-engines with low specific fuel consumption. The transmission system has indeed a direct impact on the engine overall efficiency by means of its weight contribution, internal power losses and lubrication requirements. Thus, an evaluation of its structure and performance is mandatory in order to optimize the design as well as maximize its efficiency. Gears are among the most efficient power transmission systems, whose efficiencies can exceed 99 %, nevertheless in high speed applications power losses are anything but negligible. All power dissipated through losses is converted into heat that must be dissipated by the lubrication system. More heat leads a larger cooling capacity, which results in more oil, larger heat exchangers which finally means more weight. Mechanical power losses are usually distinguished in two main categories: load-dependent and load-independent losses. The former are all those associated with the transmission of torque, while the latter are tied to the fluid-dynamics of the environment which surrounds the gears, namely windage, fluid trapping and squeezing between meshing gear teeth and inertial losses resulting by the impinging oil jets, usually adopted in high speed transmission for cooling and lubrication purposes. The relative magnitude of these phenomena is strongly dependent on the operative conditions of the transmission. While load-dependent losses are predominant at slow speeds and high torque conditions, load-independent mechanisms become prevailing in high speed applications, like in turbomachinery. Among fluid-dynamic losses, windage is extremely important and can dominate the other mechanisms. In this context, a new test rig was designed for investigating windage power losses resulting by a single spur gear rotating in a free oil environment. The test rig allows the gear to rotate at high speed within a box where pressure and temperature conditions can be set and monitored. An electric spindle, which drives the system, is connected to the gear through a high accuracy torque meter, equipped with a speedometer providing the rotating velocity. The test box is fitted with optical accesses in order to perform particle image velocimetry measurements for investigating the flow-field surrounding the rotating gear. The experiment has been computationally replicated, performing RANS simulations in the context of conventional eddy viscosity models. The numerical results were compared with experimental data in terms of resistant torque as well as PIV measurements, achieving a good agreement for all of the speed of rotations.
Time resolved PIV revealed strong instabilities in the flow field generated by the gear, highlighting the importance of performing unsteady simulations for a better modelling of this component. Results have been post-processed in terms of Fast Furier Transform (FFT) and Proper Orthogonal Decomposition (POD) in order to provide a reliable data base for future unsteady simulations.
In design phase it is important to predict the losses increase due to the lubricating oil jet impact on the spur gear varying the different geometrical and working parameters such as the jet inclination, distance and the oil mass flow rate and temperature.
For this reason the test rig was equipped with an oil control unit able to provide a controlled oil mass flow rate to a spray-bar placed within the test chamber. The oil jet can be regulated in terms of pressure and temperature, in such a way the mass flow rate can be imposed and measured by means of flow-meters. The spray-bar is equipped with a circular hole, its position can be varied as well as the inclination angle.
High speed visualizations were performed for every tested condition in order to deepen the physical understanding of the phenomena and to obtain more information on the lubrication and cooling capability. The high speed camera was placed in front of the gear exploiting an optical access while a halogen lamp was used to provide the proper lightening necessary due to the very low exposure time of the acquisitions.
In every test the power losses were also measured using the torque-meter, results were post-processed in order to insulate the torque increase due only to jet injection. The collected data were used for the validation of a simple 0D model able to well predict power losses due to jet injection under certain conditions.
Actes de conférences sur le sujet "Oil-jet Losses"
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Massini, D., T. Fondelli, B. Facchini, L. Tarchi et F. Leonardi. « Experimental Investigation on Power Losses due to Oil Jet Lubrication in High Speed Gearing Systems ». Dans ASME Turbo Expo 2017 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64703.
Texte intégralRésumé :
In order to reduce environmental and climate impact from air traffic, the main effort of aero-engine industry and research community is looking at a continuous increase in gearbox efficiency. With this kind of components every source of loss can be responsible for high heat loads; for this reason oil jet systems are used to provide proper cooling and lubrication of gears tooth surfaces. In the design phase it is important to predict the losses increase due to the lubricating oil jet impact on the spur gear, varying the different geometrical and working parameters such as the jet inclination, distance and the oil mass flow rate and temperature. An experimental investigation was carried out on a novel rotating test rig able to reproduce real engine working conditions in terms of speed, pressure and lubrication system, for a single spur gear. The rig consists of an electric spindle driving a shaft with a spur gear clamped on top. The gear is enclosed in a box where different air pressure conditions can be set and monitored. Pressure transducers and T-type thermocouples placed within the test box were used to measure the gear working conditions. The test box is also equipped with several optical accesses allowing flow field measurements or oil jet visualizations. The driving shaft is composed by two parts connected by a bearingless torquemeter equipped with a speedometer in order to perform torque losses and rotating velocity measurements. Tests were performed without the gear first, in order to separate the final value from the friction losses due to the driving shaft. Windage losses were characterized experimentally for every working condition and the results collected in a simple correlation that was used to separate the losses due to air windage from the ones due to the oil injection. An oil control unit allowed to impose the proper oil pressure and temperature conditions and to measure the mass flow rate. The oil jet was delivered by a spraybar placed within the gearbox, the jet to gear distance and relative angle were varied during the experiments. High speed visualizations were also performed for every test condition in order to deepen the physical understanding of the phenomena and to obtain more information on the lubrication capability of every jet condition. A high speed camera was placed in front of the gear exploiting an optical access while a halogen lamp was used to provide the proper lightening necessary due to the very low exposure time of the acquisitions. The wide experimental database provided, allowed the development of a simple numerical model able to well predict every losses contribution at the various working conditions.
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Fondelli, Tommaso, Antonio Andreini, Riccardo Da Soghe, Bruno Facchini et Lorenzo Cipolla. « Volume of Fluid (VOF) Analysis of Oil-Jet Lubrication for High-Speed Spur Gears Using an Adaptive Meshing Approach ». Dans ASME Turbo Expo 2015 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42461.
Texte intégralRésumé :
In high speed gearbox systems, the lubrication is generally provided using nozzles to create small oil jets that feed oil into the meshing zone. It is essential that the gear teeth are properly lubricated and that enough oil gets into the tooth spaces to permit sufficient cooling and prevent gearbox failure. A good understanding of the oil behaviour inside the gearbox is therefore desirable, to minimize lubrication losses and reduce the oil volume involved, and ensure gearbox reliability. In order to reach these objectives, a comprehensive numerical study of a single oil jet impinging radially on a single spur gear teeth has been carried out using the Volume of Fluid (VOF) method. The aims of this study are to evaluate the resistant torque produced by the oil jet lubrication, and to develop a physical understanding of the losses deriving from the oil-gear interaction, studying the droplets and ligaments formation produced by the breaking up of the jet as well as the formation of an oil film on the surface of the teeth. URANS calculations have been performed with the commercial code ANSYS FLUENT and an adaptive mesh approach has been developed as a way of significantly reducing the simulation costs. This method allows an automatic mesh refinement and/or coarsening at the air-oil interface based on the volume of fluid gradient, increasing the accuracy of the predictions of oil break-up as well as minimizing numerical diffusion of the interface. A global sensitivity analysis of adopted models has been carried out and a numerical set-up has been defined. Finally several simulations varying the oil injection angle have been performed, in order to evaluate how this parameter affects the resistant torque and the lubrication performances.
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Massini, D., T. Fondelli, B. Facchini, L. Tarchi et F. Leonardi. « Windage Losses of a Meshing Gear Pair Measured at Different Working Conditions ». Dans ASME Turbo Expo 2018 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76823.
Texte intégralRésumé :
In recent years the aero-engine community is looking towards the reduction of specific fuel consumption by increasing the efficiency of gearing systems. Considering their weight contribution, internal power losses and lubrication requirements, they have indeed a direct impact on the engine overall efficiency. Even though nowadays gears have reached very high efficiencies, over 99%, all the power dissipated through losses is converted into heat that must be removed by the lubrication system. Heat reduction is hence beneficial for minimizing lubrication system dimensions that is crucial in aero engine applications where it is mandatory to limit the weight of every component. Among the sources of loss, two main categories may be distinguished: load dependent and load independent losses. The first ones are due to the transmission of torque and have been deeply studied in the last years, the latter are related to fluid-dynamic interaction between gears and the surrounding environment, they are negligible at low pitch line velocities, but become very important in high speed applications, typical of turbomachinery. This work deals with an experimental investigation of the load independent losses due to a couple of spur meshing gears working at different conditions in presence of an oil-jet lubrication system. The test rig allows the gears to rotate, at different velocities up to 15000 rpm, in a controlled environment contained in a sealed box. Test rig pressure can be imposed (0.3–1.0 bar) and monitored as well as the oil jet conditions, in terms of mass flow rate (jet volume flow rate up to 1.65 litres per minute), temperature (80–140 °C) and inclination angle. A high precision bearing-less torque meter, equipped with a speedometer, was exploited to measure at the same time the torque losses and rotating speed. Results of the experimental survey allowed a better understanding of load independent losses at pitch line speed up to 100 m/s and in different environmental conditions.
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Johnson, Graham, Budi Chandra, Colin Foord et Kathy Simmons. « Windage Power Losses From Spiral Bevel Gears With Varying Oil Flows and Shroud Configurations ». Dans ASME Turbo Expo 2008 : Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50424.
Texte intégralRésumé :
In many aero-engines the power to drive accessories is transmitted through high speed bevel gears in a chamber in the center of the engine. The windage power loss (WPL) associated with these gears makes a significant contribution to the overall heat generation within the chamber. Shrouding the gears provides an effective method of reducing this WPL and managing the flow of lubricating oil. Experimental and computational programs at the University of Nottingham Technology Centre in Gas Turbine Transmission Systems are providing an improved understanding of shroud performance and design. This paper presents results from a pair of shrouded meshing gears run at representative speeds and oil flow in a rig with speed and torque measurement. A previously published study of a single bevel gear operating in air [1] found a reduction in torque of up to 70% from shrouding. In this work the addition of oil and the pinion gear did not lead to high torque due to the build up of oil under the shrouds, but the reduction in torque due to fitting the shrouds is significantly less than was found for the same gear in air alone. In order to isolate the various parameters, further testing with a single gear was carried out. A fully (360 degree) shrouded gear shows a big improvement over an unshrouded gear when running in air alone, but much of this benefit disappears as soon as a very small amount of oil is introduced under the shroud. This implies that the oil is recirculating under the shroud. Increasing the oil flow beyond this initial level increases the torque by the amount required to accelerate the oil mass flow up to the peripheral speed of the gear. Providing a full width slot in the shroud downstream of the oil jet allows the oil to escape without any recirculation and restores much of the benefit of the shroud. Further insight into the oil behavior is obtained from torque measurements and observations through a transparent shroud and with various slot configurations. Video observation shows evidence of a vortex flow under the shroud that carries some of the oil towards the inner diameter of the gear. The three main windage contributors, air alone, recirculation of oil under the shroud and acceleration of the feed oil are quantified and methods for achieving the optimum design are discussed.
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Ambrose, Stephen, Hervé Morvan et Kathy Simmons. « Investigation of Oil Jet Impingement on a Rotating Gear Using Lattice Boltzman Method (LBM) ». Dans ASME Turbo Expo 2018 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76371.
Texte intégralRésumé :
In the drive for greater increases in fuel efficiency and reductions in CO2 emissions from aero engines, an epicyclic reduction gearbox can be used to break the link between the turbine and fan, enabling the engine to run at a higher bypass ratio. However, even small power losses can generate significant amounts of heat, due to the high loads transmitted from the gearbox. A substantial amount of cooling is required to remove this heat and a large part of this is supplied directly to the gear face. Assessing the performance of coolants and minimising the buildup of oil in the system is therefore a critical stage in the design process. Traditionally, finite volume CFD methods have been used to compute flow and heat transfer solutions. More recently, Lagrangian methods such as Smoothed Particle Hydrodynamics (SPH) have also been applied. The Lattice Boltzman Method (LBM) is a mesoscopic particle based method which uses statistical properties of particles based at each point of a lattice to calculate flow properties. This is a fully transient method and allows for a simple and efficient derivation of LES turbulence properties. In this work the Lattice Bolztman Method is used to investigate the impingement of an oil jet on a rotating spur gear. A comparison of LBM simulations is made against published work using other methods such as SPH and CFD — utilising the Volume of Fluid method — as well as a qualitative comparison with published experimental high speed images. These all show an excellent agreement and the simulations take the same order of magnitude of computational power as 3D single phase SPH, but are fully multiphase and have LES turbulence. This method is then used to investigate how changes to the oil feed delivery rate affect the spreading of the oil jet on the gear tooth and the splashing profiles. The potential for applying this method to other scenarios, such as lubricating and cooling meshing gears, is also discussed.
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Prabhakar, Arun, Yousif Abdalla Abakr et Kathy Simmons. « Numerical Investigations to Assess the Impact of Shaft Speed on the Performance of Scoop Devices ». Dans ASME Turbo Expo 2018 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76177.
Texte intégralRésumé :
The demand for continuous and efficient lubrication in aeroengine bearing assemblies has encouraged the development of scoop based lubrication systems. Using a scooped rotor in conjunction with axial passages within the shaft, a scoop system can provide lubrication to bearings and other components at a different axial location to the oil supply jet, optimizing the use of space. The capture efficiency of a scoop system is the percentage of oil from the jet that is delivered to the desired end location. It is dependent on a number of factors such as shaft rotational speed, oil jet speed and other geometrical features. In this paper the impact of shaft speed on the capture efficiency of a scoop system is predicted numerically using Computational Fluid Dynamics (CFD). An analytical study has been also carried out to aid the understanding of the system’s behaviour. A simplified 2D geometry is used for the computational domain in the numerical simulations. The Volume of Fluid (VOF) multiphase model has been implemented to simulate the flow of oil and air. The effects of turbulence are modelled using the RNG K-ε turbulence model. Results obtained using CFD are compared to experimental results obtained from tests conducted on the same geometry. It is evident from CFD and experiments that for a fixed oil jet velocity there is an optimum shaft speed at which maximum capture efficiency is obtained. This is somewhat higher than the threshold value identified by the analytical study at which 100% capture becomes theoretically possible. Maximum capture efficiencies of around 80% are predicted. Some oil is uncaptured because it forms a plume ahead of the scoop tip and deflects outwards and some is initially captured but leaves the scoop through centrifugal effects. The analytical model suggests that the point of jet strike on the scoop may affect/control losses due to centrifugal effects with more oil being lost when the point of strike is closer to the scoop tip. Pluming losses become more significant at higher shaft speeds because the angle over which oil is captured decreases. Predicted scoop capture efficiencies obtained using CFD are within 5.5% of experimentally obtained results for the configuration investigated here. Trends in behavior are the same experimentally and computationally highlighting the usefulness of a 2D CFD modelling approach.
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Fondelli, T., D. Massini, A. Andreini, B. Facchini et F. Leonardi. « Three-Dimensional CFD Analysis of Meshing Losses in a Spur Gear Pair ». Dans ASME Turbo Expo 2018 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-77141.
Texte intégralRésumé :
The reduction of fluid-dynamic losses in high speed gearing systems is nowadays increasing importance in the design of innovative aircraft propulsion systems, which are particularly focused on improving the propulsive efficiency. Main sources of fluid-dynamic losses in high speed gearing systems are windage losses, inertial losses resulting by impinging oil jets used for jet lubrication and the losses related to the compression and the subsequent expansion of the fluid trapped between gears teeth. The numerical study of the latter is particularly challenging since it faces high speed multiphase flows interacting with moving surfaces, but it paramount for improving knowledge of the fluid behavior in such regions. The current work aims to analyze trapping losses in a gear pair by means of three-dimensional CFD simulations. In order to reduce the numerical effort, an approach for restricting computational domain was defined, thus only a portion of the gear pair geometry was discretized. Transient calculations of a gear pair rotating in an oil-free environment were performed, in the context of conventional eddy viscosity models. Results were compared with experimental data from the open literature in terms of transient pressure within a tooth space, achieving a good agreement. Finally, a strategy for meshing losses calculation was developed and results as a function of rotational speed were discussed.
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Rehman, Abid Ur, et Marwan Abdelbary. « Cost Effective Method of Installing Hydraulic Lift System Using Straddle Packers ». Dans SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205532-ms.
Texte intégralRésumé :
Abstract The oil and gas industry is still in transition due to uncertain oil prices. The lower demand in oil production has become a key challenge for oil and gas companies to drill new wells. To endure the operating expenses, producers are now searching for different advancements for the optimum utilization of the production from their existing wells. Artificial lift systems (ALS) is the most efficient technique to optimize production from the well. The main purpose of artificial lift systems is to maximize production from a candidate well. However, there are many systems applicable to a single well. Hence, the selection and design of a suitable system play a vital role in the cost optimization of the well. The hydraulic lift system is one of the primary lift systems used widely for decades and has always been given successful results, provided the selection and designs are as per the requirements of a specific well to optimize its production. The jet pump has no moving parts and most of the time can be deployed rig-less, which drastically decreases the installation cost and time for the Operator, translated consequently to decrease the well's kick-off time to start flow. This lift system can be installed in a variety of ways depending on the well's conditions and is a very effective method of lifting a well. However, if not planned and executed properly, the lift system will not be cost-effective for the client. This paper is about the installation of a jet pump in a unique method of punching a tubing with no seating and sealing profiles to get communication between casing to tubing annulus, then to install the Downhole Jet Pump along with a Straddle Packers assembly. The well 8D located in northern Iraq was drilled in 2014, mud losses were observed during drilling. The well was producing 50 BBLS every three days (after shutting down two days for pressure build-up. The jet pump was designed for this well, with tubing punch and straddle packer options. Since the jet pump system needs isolated pathways for its three different fluids, two straddle packers were used along with the jet pump itself to provide the sealing and proper pathways for the fluids. The study about the unique installation of jet pump systems will be discussed in detail alongside the field-gathered data to validate initial theoretical designs. The operational procedure and optimization technique for the well is also mentioned for a proper understanding of the whole system. The method used in this well will prove to be an economical option for lifting and producing old wells if there are no communication profiles between casing and tubing annulus.
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Lee, Sang Woo, Yong Beom Kim et Joon Sik Lee. « Flow Characteristics and Aerodynamic Losses of Film-Cooling Jets With Compound Angle Orientations ». Dans ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-038.
Texte intégralRésumé :
Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate the flow characteristics and aerodynamic loss distributions of film-cooling jets with compound angle orientations. For a fixed inclination angle of the injection hole, measurements are performed at various orientation angles to the direction of the mainstream in the case of three velocity ratios of 0.5, 1.0 and 2.0. Flow visualizations for the velocity ratio of 2.0 show that the increase in the orientation angle furnishes better film coverage on the test surface, but gives rise to large flow disturbances in the mainstream. A near-wall flow model has been proposed based on the surface flow visualizations. It has also been found from the flow measurements that as the orientation angle increases, a pair of counter-rotating vortices turn to a single strong one, and the aerodynamic loss field is closely related to the secondary flow. Even in the case of the velocity ratio of 2.0, aerodynamic loss is produced within the jet region when the orientation angle is large. Regardless of the velocity ratio, the mass-averaged aerodynamic loss increases with increasing orientation angle, the effect of which on aerodynamic loss is pronounced when the velocity ratio is large.
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Nerger, Daniel, Horst Saathoff, Rolf Radespiel, Volker Gu¨mmer et Carsten Clemen. « Experimental Investigation of Endwall and Suction Side Blowing in a Highly Loaded Compressor Stator Cascade ». Dans ASME Turbo Expo 2010 : Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22578.
Texte intégralRésumé :
The following paper describes an experimental investigation of a highly loaded stator cascade with a pitch to chord ratio of t/l = 0.6. Experiments without as well as with active flow control by means of endwall and suction side blowing were conducted. Five-hole-probe measurements in pitchwise and spanwise direction as well as endwall oil flow visualizations were carried out in order to determine the performance of the cascade and to analyze the flow phenomena occuring. To quantify the effectivity of the active flow control method, taking the additional energy input into account, corrected losses and an efficiency, which relates the difference of flow power deficit with and without active flow control to the flow power of the blowing jet itself, were evaluated. Even though an increase of static pressure rise could be achieved, a decrease of the total pressure losses was possible for a few operating points only.