The Experts below are selected from a list of 342 Experts worldwide ranked by ideXlab platform
Homer Rahnejat - One of the best experts on this subject based on the ideXlab platform.
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Transient thermal analysis of mixed-elastohydrodynamic contact of high performance transmission in a Dry Sump environment
2018Co-Authors: Ehsan Fatourehchi, Mahdi Mohammadpour, Stephanos Theodossiades, Homer RahnejatAbstract:Fuel efficiency is one of the main concerns in the optimization of modern racing transmissions. The Dry Sump transmissions are the preferred choice for high performance racing applications. While it provides adequate lubricant for gear contacts, it minimises the system churning losses, and therefore enhances the system efficiency. An important aspect is assessing its thermal performance in removing the generated frictional heat. The generated heat in the highly loaded high shear contacts of racing transmissions should be dissipated through use of directed impinging oil jets and in an air-oil mist environment. The paper presents an integrated tribological and 3D computational fluid dynamics analysis for a spur gear pair, incorporated into an overall finite element model to evaluate the quantity of generated heat and its removal rate from the rotating gear surfaces. Furthermore, the temperature distribution in the circumferential direction is predicted and used to evaluate transient temperature distribution over representative race laps. Such an approach has not hitherto been reported in literature
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thermal modelling of mixed non newtonian thermo elastohydrodynamics in Dry Sump lubrication systems
The 6th World Tribology Congress, 2017Co-Authors: Ehsan Fatourehchi, Mahdi Mohammadpour, Stephanos Theodossiades, Homer RahnejatAbstract:Improved fuel efficiency is the primary objective in the optimization of modern drivetrain systems. Recently, the Dry Sump lubrication system is regarded as the lubrication system for high performance transmission systems. Dry Sump lubrication enhances the system efficiency by reducing the churning losses, whilst providing sufficient lubrication for the tribological contacts. One of the most important aspects of any Dry Sump system is assessment of the thermal performance. The generated heat in the contacts should be dissipated through impinging jets and air-oil mist in the transmission casing in an efficient manner. The present work incorporates a tribological model and a 3D CFD model into a finite element model. The aim is to evaluate the quantity of generated heat in the lubricated gear pair contacts, as well as heat removal rate due to an impinging oil jet. Furthermore, the transient circumferential temperature distribution on gear surfaces is determined. This provides an accurate input temperature for the entrant lubricant in the gear teeth-pair contacts. Such an approach has not hitherto been reported in literature. To perform time-efficient system level analysis in the finite element model, extrapolated equations are obtained from a transient 3D CFD model using regression formulae.
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A test procedure to investigate lubricant-surface combination for high performance racing transmissions
2017Co-Authors: Ed Humphrey, Homer Rahnejat, Nick Morris, Ramin Rahmani, Greg RapsonAbstract:Compact light weight and Dry Sump (significantly reduced volume of lubricant) are the desired attributes for high performance racing transmissions, whilst improving upon efficiency and reliability remain paramount objectives. The complex multi-objective nature of this task points to an integrated approach to lubricant-mechanical system optimisation. The extreme operating conditions in racing transmissions, such as contact kinematics and thermal loading present significant tribological challenges. Thin lubricant films in non-Newtonian shear are subjected to mixed thermo-elastohydrodynamic regime of lubrication. Under these conditions boundary active lubricant species often determine the contact tribological performance rather than the bulk rheological properties of the lubricant itself. Therefore, the interaction of lubricant additive package with the contacting solid surfaces is the key to an optimised solution. The paper investigates the lubricant-surface interfacial effect upon frictional characteristics in contact conditions which are representative of gear teeth meshing conditions in high performance transmissions. The study uses pin-on-disc tribometry. As the contact conditions are mainly governed by the formation of surface-adhered tribo-films, their effect upon frictional characteristics is further investigated through use of atomic force microscopy (AFM) in lateral force mode (LFM). A test procedure is presented to benchmark lubricant additive package-surface combinations for improved tribological performance. The investigation takes into account surface material, surface topography and lubricant additive package, all of which affect the tribo-chemical absorption or bonding of a thin film to the contacting surfaces. The test protocol also includes surface chemical spectrometry and Scanning Electron Microscopy (SEM). The presented methodology has not hitherto been reported in literature
Ehsan Fatourehchi - One of the best experts on this subject based on the ideXlab platform.
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A system level computational model for thermo-tribological functioning of high-performance racing transmission with Dry Sump lubrication
2021Co-Authors: Ehsan Fatourehchi, Mahdi Mohammad-pourAbstract:Dry Sump lubrication is a key feature in transmission systems of high-performance racing applications. While it provides adequate oil for gears contact, it reduces churning losses. Moreover, provision of continuous oil for gear contacts in harsh conditions during a race, makes Dry Sump lubrication systems more reliable. One of the most important aspects of any Dry Sump system is the assessment of its thermo-tribological performance and its capability to remove the generated heat from highly loaded high shear gear contacts. In this paper, a multiphysics integrated numerical method of a Dry Sump transmission, considering a system approach is presented. The method provides a validated predictive tool to assess thermal functioning of Dry Sump lubrication systems
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Transient thermal analysis of mixed-elastohydrodynamic contact of high performance transmission in a Dry Sump environment
2018Co-Authors: Ehsan Fatourehchi, Mahdi Mohammadpour, Stephanos Theodossiades, Homer RahnejatAbstract:Fuel efficiency is one of the main concerns in the optimization of modern racing transmissions. The Dry Sump transmissions are the preferred choice for high performance racing applications. While it provides adequate lubricant for gear contacts, it minimises the system churning losses, and therefore enhances the system efficiency. An important aspect is assessing its thermal performance in removing the generated frictional heat. The generated heat in the highly loaded high shear contacts of racing transmissions should be dissipated through use of directed impinging oil jets and in an air-oil mist environment. The paper presents an integrated tribological and 3D computational fluid dynamics analysis for a spur gear pair, incorporated into an overall finite element model to evaluate the quantity of generated heat and its removal rate from the rotating gear surfaces. Furthermore, the temperature distribution in the circumferential direction is predicted and used to evaluate transient temperature distribution over representative race laps. Such an approach has not hitherto been reported in literature
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thermal modelling of mixed non newtonian thermo elastohydrodynamics in Dry Sump lubrication systems
The 6th World Tribology Congress, 2017Co-Authors: Ehsan Fatourehchi, Mahdi Mohammadpour, Stephanos Theodossiades, Homer RahnejatAbstract:Improved fuel efficiency is the primary objective in the optimization of modern drivetrain systems. Recently, the Dry Sump lubrication system is regarded as the lubrication system for high performance transmission systems. Dry Sump lubrication enhances the system efficiency by reducing the churning losses, whilst providing sufficient lubrication for the tribological contacts. One of the most important aspects of any Dry Sump system is assessment of the thermal performance. The generated heat in the contacts should be dissipated through impinging jets and air-oil mist in the transmission casing in an efficient manner. The present work incorporates a tribological model and a 3D CFD model into a finite element model. The aim is to evaluate the quantity of generated heat in the lubricated gear pair contacts, as well as heat removal rate due to an impinging oil jet. Furthermore, the transient circumferential temperature distribution on gear surfaces is determined. This provides an accurate input temperature for the entrant lubricant in the gear teeth-pair contacts. Such an approach has not hitherto been reported in literature. To perform time-efficient system level analysis in the finite element model, extrapolated equations are obtained from a transient 3D CFD model using regression formulae.
D R Chase - One of the best experts on this subject based on the ideXlab platform.
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An Experimental Investigation of Spur Gear Efficiency
Journal of Mechanical Design, 2008Co-Authors: T. T. Petry-johnson, Arda Kahraman, Aysegul Kahraman, N.e. Anderson, D R ChaseAbstract:In this study, a test methodology was developed for the measurement of spur gear efficiency under high-speed and variable torque conditions. A power-circulating test machine was designed to operate at speeds to 10,000rpm and transmitted power levels to 700kW. A precision torque measurement system was implemented, and its accuracy and repeatability in measuring torque loss in the power loop was demonstrated. Tests were conducted on gears with two values of modules and two surface roughness levels, operating in a Dry Sump jet-lubrication environment with three different gear lubricants. These tests were used to quantify the influence of these parameters on both load-dependent (mechanical), load-independent (spin), and total power loss. Trends in mechanical gear mesh efficiency and total gearbox efficiency were discussed in terms of rotational speed and transmitted torque. Finally, recommendations were made for the design of spur gear pairs, surface roughness, and lubricant selection for improved efficiency.
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experimental investigation of spur gear efficiency
ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 2007Co-Authors: T T Petryjohnson, N.e. Anderson, Aysegul Kahraman, D R ChaseAbstract:In this study, a test methodology was developed for measurement of spur gear efficiency under high-speed and variable torque conditions. A power-circulating test machine was designed to operate at speeds to 10,000 rpm and transmitted power levels to 700 kW. A precision torque measurement system was implemented and its accuracy and repeatability in measuring torque loss in the power loop was demonstrated. Tests were conducted on gears with two values of module, and two surface roughness levels, operating in a Dry Sump jet-lubrication environment with three different gear lubricants. These tests were used to quantify the influence of these parameters on load-dependent (mechanical), load-independent (spin), and total power loss. Trends in mechanical gear mesh efficiency and total gearbox efficiency were discussed in terms of rotational speed and transmitted torque. Finally, recommendations were made for the design of spur gear pairs, surface roughness, and lubricant selection for improved efficiency.Copyright © 2007 by ASME and General Motors
Rahnejat Homer - One of the best experts on this subject based on the ideXlab platform.
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Transient Thermal Analysis of Mixed-elastohydrodynamic Contact of High Performance Transmission in a Dry Sump Environment
'SAGE Publications', 2018Co-Authors: Fatourehchi Ehsan, Mohammad Pour Mahdi, Theodossiades Stephanos, Rahnejat HomerAbstract:Fuel efficiency is one of the main concerns in the optimisation of modern racing transmissions. The Dry Sump transmissions are the preferred choice for high performance racing applications. While it provides adequate lubricant for gear contacts, it minimises the system churning losses, and therefore enhances the system efficiency. An important aspect is assessing its thermal performance in removing the generated frictional heat. The generated heat in the highly loaded high shear contacts of racing transmissions should be dissipated through use of directed impinging oil jets and in an air–oil mist environment. The paper presents an integrated tribological and three-dimensional computational fluid dynamics analysis for a spur gear pair, incorporated into an overall finite element model to evaluate the quantity of generated heat and its removal rate from the rotating gear surfaces. Furthermore, the temperature distribution in the circumferential direction is predicted and used to evaluate transient temperature distribution over representative race laps. Such an approach has not hitherto been reported in literature
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A test procedure to investigate lubricant-surface combinations for high-performance racing transmissions
2017Co-Authors: Humphrey E, Rahnejat Homer, Morris N, Rahmani R, Rapson GAbstract:Compact light weight and Dry Sump (significantly reduced volume of lubricant) are the desired attributes for high performance racing transmissions, whilst improving upon efficiency and reliability remain paramount objectives. The complex multi-objective nature of this task points to an integrated approach to lubricant-mechanical system optimisation. The extreme operating conditions in racing transmissions, such as contact kinematics and thermal loading present significant tribological challenges. Thin lubricant films in non-Newtonian shear are subjected to mixed thermo-elastohydrodynamic regime of lubrication. Under these conditions boundary active lubricant species often determine the contact tribological performance rather than the bulk rheological properties of the lubricant itself. Therefore, the interaction of lubricant additive package with the contacting solid surfaces is the key to an optimised solution. The paper investigates the lubricant-surface interfacial effect upon frictional characteristics in contact conditions which are representative of gear teeth meshing conditions in high performance transmissions. The study uses pin-on-disc tribometry. As the contact conditions are mainly governed by the formation of surface-adhered tribo-films, their effect upon frictional characteristics is further investigated through use of atomic force microscopy (AFM) in lateral force mode (LFM). A test procedure is presented to benchmark lubricant additive package-surface combinations for improved tribological performance. The investigation takes into account surface material, surface topography and lubricant additive package, all of which affect the tribo-chemical absorption or bonding of a thin film to the contacting surfaces. The test protocol also includes surface chemical spectrometry and Scanning Electron Microscopy (SEM). The presented methodology has not hitherto been reported in literatur
Riccardo Russo - One of the best experts on this subject based on the ideXlab platform.
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a gear rattle model accounting for oil squeeze between the meshing gear teeth
Proceedings of the Institution of Mechanical Engineers Part D: Journal of Automobile Engineering, 2005Co-Authors: Renato Brancati, Ernesto Rocca, Riccardo RussoAbstract:AbstractIn this paper a non-linear one-degree-of-freedom model for analysis of gear rattle vibrations in automotive manual transmissions is presented. In order to take into account the damping effects owing to the oil in the gap between two teeth of a meshing gear, a simple one-dimensional model for the oil-film squeeze effects is proposed. The squeeze model assumes that the damping force is proportional to the oil viscosity and to the extension of the oil film in the plane of curvature of the teeth, which may depend on the lubrication conditions (Dry Sump, splash, bath).The results provided from several numerical simulations, carried out with reference to helical involute tooth pairs, confirm the capability of oil in reducing the high-frequency vibrations subsequent to the impact between the teeth. In particular, the influence exerted by oil viscosity and gap extension on the rattle characteristics is investigated through the analysis of the transient response of the driven gear by imposing a harmonic mo...
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A gear rattle model accounting for oil squeeze between the meshing gear teeth
'SAGE Publications', 2005Co-Authors: Renato Brancati, Ernesto Rocca, Riccardo RussoAbstract:In this paper a non-linear one-degree-of-freedom model for analysis of gear rattle vibrations in automotive manual transmissions is presented. In order to take into account the damping effects owing to the oil in the gap between two teeth of a meshing gear, a simple one-dimensional model for the oil-film squeeze effects is proposed. The squeeze model assumes that the damping force is proportional to the oil viscosity and to the extension of the oil film in the plane of curvature of the teeth, which may depend on the lubrication conditions (Dry Sump, splash, bath). The results provided from several numerical simulations, carried out with reference to helical involute tooth pairs, confirm the capability of oil in reducing the high-frequency vibrations subsequent to the impact between the teeth. In particular, the influence exerted by oil viscosity and gap extension on the rattle characteristics is investigated through the analysis of the transient response of the driven gear by imposing a harmonic motion to the driving gear
