Thermal modelling of mixed non-Newtonian thermo-elastohydrodynamics in dry sump lubrication systems

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

Microgeometrical Tooth Profile Modification Influencing Efficiency of Planetary Hub Gears

Planetary hub systems offer desired speed and torque variation with a lighter, compact and coaxial construction than the traditional gear trains. Generated friction between the mating teeth flanks of vehicular planetary hubs under varying load-speed conditions is one of the main sources of power loss. Modification of gear tooth geometry as well as controlling the contacting surface topography is the remedial action. The paper studies the effect of tooth crowning and tip relief upon system efficiency. It includes an analytical elastohydrodynamic analysis of elliptical point contact of crowned spur gear teeth. The analysis also includes the effect of direct contact of asperities on the opposing meshing surfaces. Tooth contact analysis (TCA) is used to obtain the contact footprint shape as well as contact kinematics and load distribution. A parametric study is carried out to observe the effect of gear teeth crowning and tip relief with different levels of surface finish upon the planetary hubs’ power loss

Effects of Gear Modification and Surface Finish on Planetary Gear Systems Efficiency

Planetary gear systems offer desired speed and torque variation with a compact and lighter construction than traditional gear trains. Transmission losses are one of the main concerns. Modification of gear teeth geometry is one of the remedial actions to reduce friction

Tribology of dust‐stop seals of mixing machines

Dust stop seals are widely used in powder and rubber mixing industries. Design of the sealing system requires a continuous supply of pressurised lubricant, which is not recycled because of the risk of contamination. There is also the potential of large volume leakage of oil due to poor sealing, increasing operational costs and necessitating remedial measures to avoid environmental protection. Furthermore, the seal faces are prone to failure in relatively short periods of time due to reduced gap and lubricant leakage. The paper presents an analytical method and numerical predictions based on Reynolds equation under combined hydrodynamic and hydrostatic conditions with the entrant lubricant through hydraulically loaded feedholes. The validity of these methods is ascertained through comparison with a more complex but time‐consuming solution of Navier–Stokes equations. The numerical predictions allow for determining the prevailing tribological contact conditions and assessing its suitability for evaluating the sealing performance of mixing machinery

Microgeometrical tooth profile modification influencing efficiency of planetary hub gears

Planetary hub systems offer desired speed and torque variation with a lighter, compact and coaxial construction than the traditional gear trains. Generated friction between the mating teeth flanks of vehicular planetary hubs under varying load-speed conditions is one of the main sources of power loss. Modification of gear tooth geometry as well as controlling the contacting surface topography is the remedial action. The paper studies the effect of tooth crowning and tip relief upon system efficiency. It includes an analytical elastohydrodynamic analysis of elliptical point contact of crowned spur gear teeth. The analysis also includes the effect of direct contact of asperities on the opposing meshing surfaces. Tooth contact analysis (TCA) is used to obtain the contact footprint shape as well as contact kinematics and load distribution. A parametric study is carried out to observe the effect of gear teeth crowning and tip relief with different levels of surface finish upon the planetary hubs’ power loss

Effect of Mesh Phasing on the Transmission Efficiency and Dynamic Performance of Wheel Hub Planetary Gear Sets

Transmission efficiency and refinement of planetary wheel hub gearing system are key design attributes for heavy and off-highway vehicles. Reduction of power loss, directly leading to the development of new generation ECO-axles requires analysis of gear contacting conditions for lubricated conjunctions to determine frictional performance. This is also affected by gear dynamics, which is a prerequisite for assessment of noise, vibration and harshness performance. Therefore, a combined tribo-dynamic analysis is essential. There is a dearth of such holistic analysis, particularly for the case of wheel hub planetary systems. The paper presents such an analysis, which has not hitherto been reported in literature. The inexorable interplay of transmission efficiency and noise, vibration and harshness refinement is demonstrated. The key attributes of noise, vibration and harshness refinement and transmission efficiency can pose contrary requirements and near-optimal conditions can be highlighted by mesh phasing of gearing contacts, thus alleviating the need for more complex gear teeth modifications entailing prohibitive manufacturing costs

Transient Thermal Analysis of Mixed-elastohydrodynamic Contact of High Performance Transmission in a Dry Sump Environment

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

Effect of tooth microgeometry profile modification on the efficiency of planetary hub gears

Planetary hub systems offer desired speed and torque variation with a lighter, compact and coaxial construction than the traditional gear trains. Frictional losses are one of the main concerns. Generated friction between the mating teeth flanks of vehicular planetary hubs under varying load-speed conditions is one of the main sources of power loss. Modification of gear tooth geometry as well as controlling the surface topography are the remedial actions to reduce friction and hence the power loss. The paper studies the effect of tooth crowning and tip relief upon system efficiency. It includes an analytical elastohydrodynamic analysis of elliptical point contact of crowned spur gear teeth, also including the effect of direct contact of asperities on the opposing surfaces. Tooth contact analysis (TCA) is performed to obtain contact footprint shape as well as contact kinematics and load distribution. A parametric study is carried out with the expounded model to observe the effect of gear crowning and tip relief with different levels of gear surface finish upon planetary hubs’ power loss

Prediction of frictional and thermal efficiency of high performance transmission system

Prediction of frictional and thermal efficiency of high performance transmission syste

A system level computational model for thermo-tribological functioning of high-performance racing transmission with dry sump lubrication

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