Underpinning research for aqueous lubrication in electric vehicle applications
Lead Research Organisation:
Loughborough University
Department Name: Wolfson Sch of Mech, Elec & Manufac Eng
Abstract
The electric vehicle (EV) market is growing at an unprecedented rate. EV drivelines face unique operational and reliability challenges to reduce energy consumption, increase vehicle range, and switch from oil-based lubrication.
EV lubricants face significant challenges operating inside electromagnetic fields that damage surfaces by electric discharge and changes molecular interactions at the surface. They need to lubricate under severe conditions, from low-speed high-torque to super-high speeds and angular accelerations typical of EV operation. Lubrication is in boundary-to-mixed regime where surface contact occurs, so forming protective tribofilms is paramount. Switching to aqueous lubrication has benefits to the environment, health, and increased cooling (increasingly as both lubricant and coolant combined), but brings significant challenges in film formation and corrosion. How tribofilms form and evolve in the electro-aqueous environment is fundamental to their operation.
This project aims to provide fundamental understanding of aqueous EV lubricant performance and create a framework for performance prediction in real applications, thus enabling development of appropriate sustainable lubricants. This includes mechanistic and deterministic models and novel experiments at different scales - the formation of tribofilms at molecular level, single asperity and contacts, and then to full-size bearing components.
We have designed four work packages, each for a different length scale. In WP1 we investigate commercial and prototype fluids in an electrified full-size bearing, exploring tribofilm formation, surface damage, and failure mechanisms. A component (bearing) level simulation model, built simultaneously, will incorporate contact analysis, thermo-hydrodynamic and boundary film formation. In WP2, single contact level testing is performed in bench-top simulators to closely control the contact between rolling and sliding parts, watching for tribofilm and damage mechanistic evolution, with and without potential. WP3 considers the single asperity, using AFM experiments, to study tribofilm composition and how it builds atomically at the contact. This is complemented by the molecular dynamics simulations in WP4, studying the adsorption of the candidate molecules to form boundary films and the effect of electric fields. These are then upscaled to film formation at contact and bearing scale.
The team consists of three world-leading tribology groups with complementary expertise. Loughborough have a long track record in tribodynamics, including EV transmissions. Imperial College leads the field in development of lubricant additives, transmission technologies, and modelling at all scales. Sheffield specialises in machine element experimental measurement and sensing. The industrial partners span the supply chain and are committed as this aligns with their business needs. Shell will support with their expertise in lubricant design, supply of fluids, access to test equipment, and fund a PhD. SKF will support with expertise in bearings, effect of electric potentials, as well as specialist equipment and PhD funding. Scania will provide data on EV drive cycles, and expertise in performance of EV drivelines. AVL will provide access to their simulation tools and dissemination to their customer base.
The output from the project will be a complete methodology for design and selection of aqueous lubricants for electric vehicles. This will be adopted by our industrial partners and more widely into automotive and lubricant sectors.
EV lubricants face significant challenges operating inside electromagnetic fields that damage surfaces by electric discharge and changes molecular interactions at the surface. They need to lubricate under severe conditions, from low-speed high-torque to super-high speeds and angular accelerations typical of EV operation. Lubrication is in boundary-to-mixed regime where surface contact occurs, so forming protective tribofilms is paramount. Switching to aqueous lubrication has benefits to the environment, health, and increased cooling (increasingly as both lubricant and coolant combined), but brings significant challenges in film formation and corrosion. How tribofilms form and evolve in the electro-aqueous environment is fundamental to their operation.
This project aims to provide fundamental understanding of aqueous EV lubricant performance and create a framework for performance prediction in real applications, thus enabling development of appropriate sustainable lubricants. This includes mechanistic and deterministic models and novel experiments at different scales - the formation of tribofilms at molecular level, single asperity and contacts, and then to full-size bearing components.
We have designed four work packages, each for a different length scale. In WP1 we investigate commercial and prototype fluids in an electrified full-size bearing, exploring tribofilm formation, surface damage, and failure mechanisms. A component (bearing) level simulation model, built simultaneously, will incorporate contact analysis, thermo-hydrodynamic and boundary film formation. In WP2, single contact level testing is performed in bench-top simulators to closely control the contact between rolling and sliding parts, watching for tribofilm and damage mechanistic evolution, with and without potential. WP3 considers the single asperity, using AFM experiments, to study tribofilm composition and how it builds atomically at the contact. This is complemented by the molecular dynamics simulations in WP4, studying the adsorption of the candidate molecules to form boundary films and the effect of electric fields. These are then upscaled to film formation at contact and bearing scale.
The team consists of three world-leading tribology groups with complementary expertise. Loughborough have a long track record in tribodynamics, including EV transmissions. Imperial College leads the field in development of lubricant additives, transmission technologies, and modelling at all scales. Sheffield specialises in machine element experimental measurement and sensing. The industrial partners span the supply chain and are committed as this aligns with their business needs. Shell will support with their expertise in lubricant design, supply of fluids, access to test equipment, and fund a PhD. SKF will support with expertise in bearings, effect of electric potentials, as well as specialist equipment and PhD funding. Scania will provide data on EV drive cycles, and expertise in performance of EV drivelines. AVL will provide access to their simulation tools and dissemination to their customer base.
The output from the project will be a complete methodology for design and selection of aqueous lubricants for electric vehicles. This will be adopted by our industrial partners and more widely into automotive and lubricant sectors.
