Journal articles on the topic 'Oil-jet Losses'
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1
Fondelli, Tommaso, Antonio Andreini, Riccardo Da Soghe, Bruno Facchini, and 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.
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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.
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Wang, Lin, Ze-kai Du, Yong Wang, Zhi-zhen Zheng, and 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 (February 1, 2023): 024902. http://dx.doi.org/10.1063/5.0098729.
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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 (April 5, 2022): 181–92. http://dx.doi.org/10.21122/1029-7448-2022-65-2-181-192.
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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) (December 28, 2020): 31–40. http://dx.doi.org/10.31471/1993-9973-2020-4(77)-31-40.
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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, and Ajit Shinde. "Exergy Criteria of Performance of Waste Heat Recovery Applied for Marine Auxiliary Boiler." International Journal of Heat and Technology 40, no. 1 (February 28, 2022): 297–303. http://dx.doi.org/10.18280/ijht.400135.
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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) (December 30, 2019): 24–34. http://dx.doi.org/10.31471/1993-9973-2019-4(73)-24-34.
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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, and 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 (December 29, 2017): 541–52. http://dx.doi.org/10.1177/1350650117750806.
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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, and Joon Sik Lee. "Flow Characteristics and Aerodynamic Losses of Film-Cooling Jets With Compound Angle Orientations." Journal of Turbomachinery 119, no. 2 (April 1, 1997): 310–19. http://dx.doi.org/10.1115/1.2841114.
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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, and Madhavi Vedera. "Equity research and valuation: Jet Airways." Emerald Emerging Markets Case Studies 7, no. 2 (June 5, 2017): 1–28. http://dx.doi.org/10.1108/eemcs-06-2016-0144.
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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 (November 2007): 37–42. http://dx.doi.org/10.4028/www.scientific.net/amr.29-30.37.
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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.
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Raghu, P., Michael S. Mukilan, R. Bharath Viswanath, S. Audithya Krishna, and N. Nallusamy. "Experimental Study on the Spray Characteristics of Diesel and Biodiesel (Jatropha Oil) in a Spray Chamber." Advanced Materials Research 768 (September 2013): 180–87. http://dx.doi.org/10.4028/www.scientific.net/amr.768.180.
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The increasing industrialization and motorization of the world has led to a steep rise for the demand of petroleum-based fuels. Petroleum based fuels are obtained from limited reserves highly concentrated in certain regions of the world i.e. those countries that lack these resources are facing energy crisis. Hence it is necessary to look for alternative fuels which can be produced from resources available locally within the country such as biodiesel, alcohol and vegetable oil. The biodiesel is technically competitive with conventional petroleum derived diesel fuel and requires no changes in the fuel distribution system. For this reason and its biodegradability, use of biodiesel is considered a good alternative of fossil fuels. Injection process of biodiesel influences the atomization and dispersion of fuel in the combustion chamber. In this research work the influence of biodiesel on injection process and their impact on the air-fuel mixture preparation are studied. Spray characteristics of biodiesel (Jatropha oil) and diesel under various injection pressures were studied experimentally. Spray penetration and spray angle were measured in a spray vessel using a high speed video camera. The study shows the biodiesel gives longer spray tip penetration and spray angle are smaller than those of diesel fuels. The parameters like break up time and break up velocity were for biodiesel and diesel at various injection pressures. It was found that breakup time for biodiesel increases and breakup velocity decreases. Breakup velocity of biodiesel is less than diesel, this is due to higher sound velocity, density, viscosity and bulk modulus of biodiesel. High viscosity fuel suppresses the instabilities required for fuel jet to breakup and thus delays atomization and reduces fuel losses during injection. With the increase in fuel injection pressure, the breakup time for biodiesel is more than diesel, this is due its larger surface area of the spray and larger mixing time of biodiesel than diesel.
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Jeхenov M.K.,, Ismagilov F.R.,, Akhmetov S.M.,, Diarov M.,, and Bektay Y.K.,. "UTILIZATION OF HYDROGEN SULFIDE-CONTAINING REFINERY FLARE GASЕS." SERIES CHEMISTRY AND TECHNOLOGY 5, no. 443 (October 15, 2020): 64–70. http://dx.doi.org/10.32014/2020.2518-1491.81.
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Modern oil refinery flare does not provide the beneficial use of discharged hydrocarbon gases and vapors, which does not allow to reduce the volume of hydrocarbon gas burned in flare candles and reduce atmospheric pollution. To ensure a stable and trouble-free operation of the flare plant and to increase the efficiency of waste gas utilization, their preliminary compression using mechanical or jet compressors and the construction of gas treatment plants are required. A low-cost method of utilizing hydrogen sulfide-containing refinery gas is proposed, including two-stage gas compression by a liquid-ring compressor using an alkanolamine aqueous solution as a working fluid in the first stage of compression, separation of the compressor of first stage compression to produce desulfurized gas, hydrocarbon condensate and an alkanolamine saturated hydrogen sulfide. In the second stage, the compression of the desulfurized gas is carried out by a liquid-ring compressor using a hydrocarbon absorbent as the working fluid, cooling and separation of the compress of the second stage of compression produce lean gas, water condensate and absorbate. The aqueous condensate is mixed with saturated hydrogen sulfide alkanolamine absorbent and taken out for regeneration, the hydrocarbon condensate is mixed with the absorbate to produce BFLH, and the lean gas is subjected to membrane separation to produce hydrogen and fuel gas. Application of the method can partially cover the needs of refineries in hydrogen by reducing its losses, as well as return gas and hydrocarbon fractions for processing or to the fuel network of the plant.
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Darian, Leonid A., Vladimir P. Polistchook, and Alexey V. Shurupov. "Testing of models of explosion protection system for highvoltage oil-filled electrical equipment." Journal of Energy - Energija 63, no. 1-4 (July 4, 2022): 156–65. http://dx.doi.org/10.37798/2014631-4174.
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Explosions of high voltage oil-filled electrical equipment (OFEE) lead to a significant material damage. These explosions occur under action of an arc discharge (AD) which arises after internal short circuit. Modernization of OFEE design and protection systems is the possible way to achieve significant reduction of potential explosion and substantial reduction of material losses. Examination of perspective explosion-proof OFEE designs and new explosion protection systems demands the effective test methods. In present work results of development and application of an arcless source of pulse pressure (ASPP) are described. In ASPP the testing impulse is produced by the jet of powder gases (JPG) which arises at the combustion of explosive materials. In this work results of experimental researches of AD in transformer oil (TO) at conditions typical for AD initial stage have been presented: current rise time was 3-5 ms, the maximum arc current was up to 30 kA, AD burning time was 3-20 ms. The energy released in AD amounted to 0.1 MJ. It was established, that electric field strength in AD column was about 0.2 kV/сm, gas producing factor in AD was 110 l/MJ, growth rate of pressure in TO was about 0.3 MPa/ms. These results allowed to create an ASPP with demanded parameters. Experiments proved that TO flow under action of AD and JPG are similar given that the same influence duration of the energy released in AD is equalled enthalpy of JPG at liquid inlet. In this work the transformer fracturing behavior after explosion has been analyzed; and the requirements for protection systems have been formulated. By means of ASPP the breadboard model tests of two well-known OFEE explosion protection methods were carried out. In the first method it is assumed that the protection is reached due to fast dump of pressure inside of OFEE case when special membranes are opened. In the second protection method it is offered to establish porous coverings on internal surfaces of OFEE cases. Experiments were carried out on OFEE model with the characteristic size of 1 m at action energy up to 1.5 MJ. It was shown, that these systems cannot protect the transformer body from significant damages. The dynamic protection system of transformer (DPS) has been described. The efficiency of this new system using ASPP has been verified in experiments with autotransformer of 25 MW. It was shown that DPS protects the transformer from considerable damages at least at dynamic impulse of about 3 MJ.
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Monieta, Jan. "Method and a Device for Testing the Friction Force in Precision Pairs of Injection Apparatus of the Self-Ignition Engines." Energies 15, no. 19 (September 21, 2022): 6898. http://dx.doi.org/10.3390/en15196898.
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This article reviews the state of the knowledge and technology in the field of friction-loss measurements in internal combustion piston engines. The dependencies that describe the loss of energy in combustion engines and injection apparatus are presented. Currently, very little can be found in the literature on the study of frictional forces in injection apparatus, but mainly in the piston–cylinder group, so this work significantly fills that gap. The aim of this article is to construct a device and to develop a method for assessing the technical state of injector nozzles to minimize friction losses in internal combustion engines at the stages of evaluation, design, production and operation. This article presents a stand for determining the maximum friction forces due to gravity loading by water-jet control. This article also presents test results on the maximum friction force between a needle and a body of injector nozzles in piston combustion engines on a designed and purpose-built stand outside of the combustion engine. Various designs and injector nozzles are made from various types of alloy steel for marine and automotive piston internal combustion engines fueled with distillation or residual fuels, and are tested. The research concerned conventional elements for the injection apparatus as well as electronically controlled subsystems. Precision pairs of injection equipment are selected for the tests: new ones are employed after the storage period and operated in natural conditions. The elements dismantled from the internal combustion engines are tested in the presence of fuel or calibration oil of similar properties. The maximum static frictional forces under the hydrostatic loading are measured, alongside the parameters for the dynamic movement of the nozzle needles from bodies of the injector nozzle as time, speed, acceleration and dynamic force. The influence of the angular position of the needle in relation to the bodies of the precision pairs conventional internal combustion engines, the diametral clearance between the nozzle body and needle, and the surface conditions on the values of the maximum friction force are also presented. Errors in shape and position result in the uniqueness of the friction force at the mutual angular position of the needle in relation to the nozzle body, and the decrease in diametral clearance and deterioration of the surface state increase the friction losses. A model was elaborated of the influence of various factors on the value of the maximum friction force.
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Barker, R., X. Hu, A. Neville, and S. Cushnaghan. "Empirical Prediction of Carbon-Steel Degradation Rates on an Offshore Oil and Gas Facility: Predicting CO2 Erosion-Corrosion Pipeline Failures Before They Occur." SPE Journal 19, no. 03 (April 23, 2013): 425–36. http://dx.doi.org/10.2118/163143-pa.
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Summary Various sections of carbon-steel pipework removed from an offshore facility were found to have experienced severe degradation, partly attributed to an insufficient inhibitor dose rate, as discussed in a previous case study (Hu et al. 2011b). An investigation was conducted to compare the predictive capability of an empirical model generated with data from a submerged-impinging-jet laboratory apparatus. The model was assessed in its ability to determine the rate of thickness loss for carbon-steel pipework subjected to a CO2-containing erosion-corrosion environment, reviewing to what extent the prediction agrees with inspection data. The investigation considers whether the developed tool could have predicted pipework failures on the facility, comparing it with the degradation rate calculated from a leak that occurred within the past 2 years. The program of experiments set out to create a means of prediction with the material-loss data from submerged-impinging-jet tests over a range of conditions replicating those within the line. Information pertaining to the temperature, production rate, and sand loading was collated for the offshore facility. These data were used along with mass-loss results to predict the degradation rate on the asset as a function of time over a 5-year period. This in turn was used to predict the total thickness loss of the pipework wall as a function of time. Consideration was also given to the current use of inhibition (10 ppm Inhibitor A) as well as the predicted thickness losses as a function of time had a candidate inhibitor been used instead (50 ppm Inhibitor B). Limitations of the model are presented, along with suggestions for ways to develop the model further.
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Matos, Pedro. "2012 Fuel Hedging at JetBlue Airways." Darden Business Publishing Cases, January 20, 2017, 1–23. http://dx.doi.org/10.1108/case.darden.2016.000003.
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In early 2012, an equity analyst, was examining the jet fuel hedging strategy of JetBlue Airways for the coming year. Because airlines cross-hedged their jet fuel price risk using derivatives contracts on other oil products such as WTI and Brent crude oil, they were exposed to basis risk. In 2011, dislocations in the oil market led to a Brent-WTI premium wherein jet fuel started to move with Brent instead of WTI, as it traditionally did. Faced with hedging losses, several U.S. airlines started to change their hedging strategies, moving away from WTI. But others worried that the Brent-WTI premium might be a temporary phenomenon. For 2012, would JetBlue continue using WTI for its hedges, or would it switch to an alternative such as Brent?
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Quiban, Romain, Christophe Changenet, Yann Marchesse, and Fabrice Ville. "Experimental Investigations About the Power Loss Transition Between Churning and Windage for Spur Gears." Journal of Tribology 143, no. 2 (August 24, 2020). http://dx.doi.org/10.1115/1.4047949.
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Abstract Oil sump lubrication is commonly used in gearboxes. When considering consistent speeds, oil immersion is usually set to low level in order to reduce associated power losses. This configuration is already used in some parts of helicopter mechanical transmissions, and it is under consideration as a lubrication solution for future electric powertrain where gearbox input speeds may be very high. The gear drag power losses are generally evaluated from either a churning power loss model for classic oil sump lubrication or a windage power loss model for oil jet lubrication. One may thus wonder how to estimate drag losses when considering a gear that only a small part is immersed. In this study, the authors investigate the transition between churning and windage phenomena for a spur gear. A series of torque measurements on a single spur gear rotating in an oil bath at numerous oil immersion levels have been carried out. Based on these results, a criterion to indicate which power loss model to use is proposed.
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Fatourehchi, Ehsan, Hamed Shahmohamadi, Mahdi Mohammadpour, Ramin Rahmani, Stephanos Theodossiades, and Homer Rahnejat. "Thermal Analysis of an Oil Jet-Dry Sump Transmission Gear Under Mixed-Elastohydrodynamic Conditions." Journal of Tribology 140, no. 5 (April 26, 2018). http://dx.doi.org/10.1115/1.4039567.
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Improved fuel efficiency and reduced emissions are key drivers for modern drivetrain systems. Therefore, in recent years, dry sumps with air–oil mist lubrication have been used for efficient transmission design in order to reduce the churning losses. With dry sumps, appropriate cooling measures should be implemented to dissipate the generated contact heat in an efficient manner. This paper integrates a tribological model with three-dimensional (3D) thermofluid analysis in order to predict the heat generated in the lubricated meshing gear contacts and its dissipation rate by an impinging oil jet in air–oil mist environment. Such an approach has not hitherto been reported in literature. The results show that the generated heat under realistic conditions cannot be entirely dissipated by the impinging oil jet in the air–oil mist transmission casing. Numerical results are used to derive extrapolated regressed equations for heat transfer purposes for time-efficient analysis. These conform well with the detailed numerical results.
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Brossier, P., D. Niel, C. Changenet, F. Ville, and J. Belmonte. "Experimental and numerical investigations on rolling element bearing thermal behaviour." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, June 9, 2020, 135065012093233. http://dx.doi.org/10.1177/1350650120932335.
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In the present study, some measurements have been conducted on a dedicated test rig to investigate rolling element bearing thermal behaviour. This test rig makes possible the determination of the tested rolling element bearing power losses through the resistive torque measurement. Some thermocouples are located on fixed parts of the system (housing, rolling element bearing outer ring) and others on rotating parts (rolling element bearing inner ring and shaft) via a telemetry system. A deep groove ball bearing, whose pitch diameter is equal to 85 mm, has been tested under oil jet lubrication for different operating conditions. Measurements of the penetration ratio, defined as the proportion of oil actually entering the rolling element bearing versus the oil injected, have also been conducted. An extended thermal network of the test rig has been established to enable a closer understanding of the rolling element bearing inner thermal behaviour. Based upon the first principle of thermodynamics for transient conditions, the studied system is divided into lumped elements at uniform temperature connected by thermal resistances which account for conduction, radiation and convection. Convection within the rolling element bearing depends on the amount of oil in the oil–air mixture known as the volume fraction. At specific test conditions, the developed model found good agreements with experiences for a given oil volume fraction of 15%. This value of volume fraction leads to an adapted formula for volume fraction in the case of jet lubrication which includes the measured penetration ratio.
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Johnson, Graham, Budi Chandra, Colin Foord, and Kathy Simmons. "Windage Power Losses From Spiral Bevel Gears With Varying Oil Flows and Shroud Configurations." Journal of Turbomachinery 131, no. 4 (July 13, 2009). http://dx.doi.org/10.1115/1.3072519.
Full textAbstract:
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 the 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 (Johnson et al., 2007, “Experimental Investigation Into Windage Power Loss From a Shrouded Spiral Bevel Gear” ASME Paper No. GT2007-27885) 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 buildup 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 deg) 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 toward 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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Nerger, Daniel, Horst Saathoff, Rolf Radespiel, Volker Gümmer, and Carsten Clemen. "Experimental Investigation of Endwall and Suction Side Blowing in a Highly Loaded Compressor Stator Cascade." Journal of Turbomachinery 134, no. 2 (June 23, 2011). http://dx.doi.org/10.1115/1.4003254.
Full textAbstract:
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 directions 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 occurring. 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.
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Beck, Christopher, Jürgen Schorr, Harald Echtle, Jasmin Verhagen, Annette Jooss, Christian Krüger, and Michael Bargende. "Numerical and experimental investigation of flow phenomena in rotating step-holes for direct-spray-cooled electric motors." International Journal of Engine Research, June 6, 2020, 146808742091804. http://dx.doi.org/10.1177/1468087420918046.
Full textAbstract:
Despite their high efficiency, electric motors are thermally limited in some operating points by several types of losses. Whenever temperature–critical components threaten to overheat, the performance is reduced for component protection (derating). The use of a suitable cooling concept may reduce the derating. The design of efficient cooling concepts of electric motors in traction drives with increased power densities is challenging, caused by the fact that the heat releases in the components vary considerably with the operating point. One option to reduce the temperatures is to place the heat sinks close to heat sources. Therefore, direct spray cooling with nozzles located in the rotor shaft is often used for cooling the end windings. The dielectric fluid (e.g. oil) is introduced into the mainly air-filled interior of the electric motor. In the following study, the behavior of the jet in the rotating step-holes at different volumetric flow rates is examined. To carry out the investigation, a new test rig and a novel optically accessible electric motor were designed. In this specifically designed test environment, the shape of the jets of different operating points is investigated by direct high-speed visualization. The cinematography setup is made of a four-light-emitting diode system in combination with a high-speed camera. A combined approach of experiment and simulation is used to find basic mechanisms of spray formation produced by rotating step-holes. Depending on the volumetric flow rate and the rotational speed, the direction of the oil jet gets more curved in relation to the rotating nozzle after exiting the small bore. If the deflection is large, the jet impinges on the wall of the large bore before reaching the end of the nozzle. The jet formation at the exit of the step-hole is mainly driven by the divergent forces in the liquid caused by impingement and the counteracting Coriolis force. Depending on the volumetric flow rate with constant rotational speed, different cross-sectional shapes of the jet at the exit are observed. These characteristic shapes can be grouped as a round undisturbed jet, strands with a connecting lamella and a C-shaped cross-section.
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von Plehwe, Felix C., Corina Schwitzke, and Hans-Jörg Bauer. "Heat Transfer Coefficient Distribution on Oil Injection Cooled Gears: Experimental Method, Uncertainty and Results." Journal of Tribology, December 5, 2020, 1–25. http://dx.doi.org/10.1115/1.4049262.
Full textAbstract:
Abstract To design gearboxes with very high power densities, an effective means of cooling the gears and knowledge of the achievable heat transfer coefficients are necessary. In this paper, a method to measure heat transfer coefficients for oil injection cooled gears is presented. Contrary to other experimental investigations, a single hollow spur gear is used. To measure heat transfer coefficients, a temperature gradient between the gear and the hot oil needs to be induced. This is achieved by injecting hot oil at realistic temperatures and cooling the inside diameter of the gear. This enables the measurement of heat transfer coefficients in absence of any dissipative or frictional losses, decreasing the measurement uncertainty. In addition, the novel method yields spatially resolved HTC data. The uncertainty of the method is assessed using Monte Carlo simulations. Experimental results for various operating conditions are presented. For all investigated oil flow rates, the same characteristic behavior of average heat transfer coefficient versus rotational speed was observed. This observation can be explained by using a kinematic model of the oil jet. The geometry of the gear and the cooling arrangement as well as the spatially resolved HTC data presented in this paper provide a complete basis for the validation of numerical simulations.
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Dadouche, Azzedine, and Rami Kerrouche. "Bearing Skidding Detection for High Speed and Aero Engine Applications." Journal of Engineering for Gas Turbines and Power, September 14, 2021. http://dx.doi.org/10.1115/1.4052428.
Full textAbstract:
Abstract Rolling-element bearings (REB) can develop severe damage due to skidding (slipping) between the rolling elements and bearing races. Skidding can be described as gross sliding between the bearing surfaces in relative motion and can result in significant surface distress such as smearing, especially at light loads and high rotational speeds. Under these conditions, skidding occurs between the rolling elements and the bearing races, leading to increased wear (higher friction coefficient), elevated bearing temperature, significant power losses and reduced service life of the bearing. The main objective of this study is to investigate the significance of various sensing technologies (induction, vibration, ultrasound, acoustic and optical) in detecting skidding in standard series roller bearings as well as custom-made roller bearings for aero engine applications. The bearings have a bore diameter of 60 mm and 90 mm, respectively. Jet and under race lubrication techniques have been used to supply oil to the bearings under test. The custom-made aero engine test bearing features special channels to allow under race lubrication of the rollers/races contacts as well as the cage land. The effect of radial load, rotational speed and oil flow on roller skidding have also been investigated and analyzed. Tests have been performed on a dedicated high speed experimental bearing facility and data was recorded using a commercially-available data acquisition system.