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Author: Amir Aleem Hashmi Publisher: Logos Verlag Berlin GmbH ISBN: 3832532285 Category : Science Languages : en Pages : 162
Book Description
Aero engine bearing chambers are complex machine elements inside the engines, supporting up to three concentric shafts on bearings. For safety reasons, the aero engines always employ rolling-element type bearings and therefore require a sufficient oil supply for lubrication in order to guarantee a reliable operation. As a consequence, a complex two-phase flow consisting of oil and sealing air governs the bearing chambers. A highly dynamic oil film, flowing along the chamber walls, plays a vital role to fulfill the tasks of cooling, lubricating and cleaning the bearing chambers. The design and optimization process of the bearing chambers requires a detailed understanding in order to accurately simulate the film behaviour inside the bearing chambers. Based on the earlier experimental investigations, it is known that near the scavenge off-take a relatively thick film exists. The numerical model to simulate these films must therefore take into account the elliptical behaviour of such films. Among the different models, the Volume Of Fluid (VOF) Model offers the best compromise between accuracy and efforts. However, preliminary attempts to model a fully developed and turbulent test case from literature revealed an unphysical pressure drop and velocity profile in the gas phase above the film flow. An inadequate turbulence modelling near the gas-liquid interface was identified as the problem source. The 2-Equation turbulence models (k- epsilon & k- omega) were extended to achieve a substantial improvement.
Author: Amir Aleem Hashmi Publisher: Logos Verlag Berlin GmbH ISBN: 3832532285 Category : Science Languages : en Pages : 162
Book Description
Aero engine bearing chambers are complex machine elements inside the engines, supporting up to three concentric shafts on bearings. For safety reasons, the aero engines always employ rolling-element type bearings and therefore require a sufficient oil supply for lubrication in order to guarantee a reliable operation. As a consequence, a complex two-phase flow consisting of oil and sealing air governs the bearing chambers. A highly dynamic oil film, flowing along the chamber walls, plays a vital role to fulfill the tasks of cooling, lubricating and cleaning the bearing chambers. The design and optimization process of the bearing chambers requires a detailed understanding in order to accurately simulate the film behaviour inside the bearing chambers. Based on the earlier experimental investigations, it is known that near the scavenge off-take a relatively thick film exists. The numerical model to simulate these films must therefore take into account the elliptical behaviour of such films. Among the different models, the Volume Of Fluid (VOF) Model offers the best compromise between accuracy and efforts. However, preliminary attempts to model a fully developed and turbulent test case from literature revealed an unphysical pressure drop and velocity profile in the gas phase above the film flow. An inadequate turbulence modelling near the gas-liquid interface was identified as the problem source. The 2-Equation turbulence models (k- epsilon & k- omega) were extended to achieve a substantial improvement.
Author: Davide Peduto Publisher: Logos Verlag Berlin GmbH ISBN: 3832540016 Category : Science Languages : en Pages : 206
Book Description
Bearing Chambers in Aero-Engines are located near the rolling-element type of bearings which support the shafts and accomodate the resulting thrust loads. One of the main task of the bearing chambers is, beside an efficient scavenging of the lubricating oil, the cooling of the hot compartments. A very complex two-phase air-oil flow takes usually place in these bearing chambers consisting of oil droplet-laden air flows and shear-driven liquid wall films. The interaction of the droplets with the wall films is significantly influencing the wall heat transfer and the cooling performance of these systems. For this reason, a detailed characterization and modelling of the mass and momentum exchange between droplets and wall films for the unique impingement parameter range in bearing chambers is inevitable. This scientific report investigates the oil droplet impact dynamics for typical impingement regimes relevant to aero-engine bearing chambers. The application of a Direct Numerical Simulation (DNS) technique based on the Volume-of-Fluid (VOF) method and coupled with a gradient-based adaptive mesh refinement (AMR) technique allowed to characterize the drop impact dynamics during various single micro- and millimeter drop impacts onto thin and thick films. With the help of a special numerical treatment, a self-perturbing mechanism is installed that leads to the correct resolution of the crown disintegration process. The numerical methodology was thoroughly validated using the experimental results of millimeter sized drop impacts onto deep liquid pools. These results were developed with an enhanced back-illuminated high-speed imaging and Particle Tracking Velocimetry (PTV) technique. New insights into the cavity penetration, the crown's breakup dynamics and the secondary droplet characteristics following a single drop impact have been developed with the help of the isolated variation of different parameters of influence. Particularly the influence of the Froude number, the impingement angle, and the cavity-wall interaction delivered results to date not reported in scientific literature. Beside the advances in fundamental physics describing the drop impact dynamics with the help of the numerical and experimental results, a set of correlations could also be derived. From these correlations, a drop-film interaction model was formulated that is suitable for the parameter range found in bearing chambers.
Author: Amir A. Hashmi Publisher: ISBN: 9783832593650 Category : Electronic book Languages : en Pages : 164
Book Description
Annotation Aero engine bearing chambers are complex machine elements inside the engines, supporting up to three concentric shafts on bearings. For safety reasons, the aero engines always employ rolling-element type bearings and therefore require a sufficient oil supply for lubrication in order to guarantee a reliable operation. As a consequence, a complex two-phase flow consisting of oil and sealing air governs the bearing chambers. A highly dynamic oil film, flowing along the chamber walls, plays a vital role to fulfill the tasks of cooling, lubricating and cleaning the bearing chambers. The design and optimization process of the bearing chambers requires a detailed understanding in order to accurately simulate the film behaviour inside the bearing chambers. Based on the earlier experimental investigations, it is known that near the scavenge off-take a relatively thick film exists. The numerical model to simulate these films must therefore take into account the elliptical behaviour of such films. Among the different models, the Volume Of Fluid (VOF) Model offers the best compromise between accuracy and efforts. However, preliminary attempts to model a fully developed and turbulent test case from literature revealed an unphysical pressure drop and velocity profile in the gas phase above the film flow. An inadequate turbulence modelling near the gas-liquid interface was identified as the problem source. The 2-Equation turbulence models (k- epsilon & k- omega) were extended to achieve a substantial improvement.
Author: Francesco Montomoli Publisher: Springer ISBN: 3319929437 Category : Technology & Engineering Languages : en Pages : 204
Book Description
This book introduces design techniques developed to increase the safety of aircraft engines, and demonstrates how the application of stochastic methods can overcome problems in the accurate prediction of engine lift caused by manufacturing error. This in turn addresses the issue of achieving required safety margins when hampered by limits in current design and manufacturing methods. The authors show that avoiding the potential catastrophe generated by the failure of an aircraft engine relies on the prediction of the correct behaviour of microscopic imperfections. This book shows how to quantify the possibility of such failure, and that it is possible to design components that are inherently less risky and more reliable. This new, updated and significantly expanded edition gives an introduction to engine reliability and safety to contextualise this important issue, evaluates newly-proposed methods for uncertainty quantification as applied to jet engines. Uncertainty Quantification in Computational Fluid Dynamics and Aircraft Engines will be of use to gas turbine manufacturers and designers as well as CFD practitioners, specialists and researchers. Graduate and final year undergraduate students in aerospace or mathematical engineering may also find it of interest.
Author: Norman Rhodes Publisher: John Wiley & Sons ISBN: Category : Science Languages : en Pages : 216
Book Description
Papers from a recent seminar discuss challenging applications in computational fluid dynamics (CFD) and identify techniques which are likely to occur in the next generation of codes. Specific topics include numerical accuracy in CFD, comparison of a conventional RANS and a lattice gas dynamics simulation, the validation of rapid CFD modeling for turbomachinery, and numerical determination of windage losses on high-speed rotating discs. Other subjects include using CFD to investigate combustion in a cement manufacturing process, validation of the coal combustion capability in the star-CD code, blast wave simulation, and built environments using CFD. Rhodes is chairman of the Institution of Mechanical Engineers' Energy Transfer and Thermofluid Mechanics Group. Distributed by ASME. c. Book News Inc.
Author: Zishun Liu Publisher: World Scientific ISBN: 1783266864 Category : Technology & Engineering Languages : en Pages : 149
Book Description
Frontiers in Applied Mechanics is a compilation of cutting-edge research in applied mechanics by 65 of the world's leading researchers and academics. It comprises current new research directions and topics in the field, as well as developments in the classical branches of applied mechanics; namely solid mechanics, fluid mechanics, thermodynamics, and materials science. Frontiers in Applied Mechanics also includes contributions from new emerging areas such as nanomechanics, biomechanics, electromechanics, the mechanical behavior of advanced materials, mechanics of soft materials, and many other inter-disciplinary research areas in which the concepts of applied mechanics are extensively applied and developed. The mathematical modeling and methodology for applied mechanics are also included, with applications to many interesting mechanics aspects. All articles were carefully selected following a thorough review process by peers.The aim of this collection is to contribute to knowledge in all aspects of applied mechanics; to improve the reader's understanding of the topics and aid their corresponding advances in the field. Readers may also use the contents as a guide for future research directions.
Author: United States. National Aeronautics and Space Administration Scientific and Technical Information Division Publisher: ISBN: Category : Corrosion and anti-corrosives Languages : en Pages : 262
Author: Amir Aleem Hashmi
Author: Amir Aleem Hashmi
Author: Davide Peduto
Author: Amir A. Hashmi
Author: Francesco Montomoli
Author: Norman Rhodes
Author: 
Author: Zishun Liu
Author: 
Author: 
Author: United States. National Aeronautics and Space Administration Scientific and Technical Information Division