Novel Robust Power Dense Motor e-Fluid Cooling Concepts
As electric vehicles evolve, the drive to create more compact, powerful and cost-efficient powertrains is in full swing. The challenge is simple to describe: powertrains must be able to manage the same power levels , but in an increasingly smaller space and lower weight, making heat management critical. This is where innovative oil-based cooling technologies will play a crucial role. Direct oil cooling has the potential to increase the power density by 50% compared to traditional water-cooled solutions. Moreover, the use of dielectric fluids (e-fluids) is inherently safer than water-based systems, which pose risks such as short circuits due to leakage. However, integrating these advanced cooling technologies is not without its challenges.
A first challenge lies in compatibility. We need to ensure that the cooling oil is compatible with all materials in the powertrain. An EV's powertrain consists of a wide range of materials, including copper conductors, plastics and specialized coatings. Each of these materials can interact differently with cooling oils, potentially leading to degradation that can compromise the integrity and functionality of the vehicle.
The second challenge has to do with robust sealing, to keep oil from creeping into the air gap. Oil cooling creates complex jet flows, which can cause a major problem if oil can creep into the air gap to cause high friction losses which increase sharply at higher rotational speeds.
Our mission lies in developing, testing and validating a robust oil coooling strategy.
Compatibility: Collaboration with Lubrizol
To address this issue, we called on the expertise of fluid technologists at Lubrizol. Our collaboration resulted in a series of rigorous tests and analyses to map the ageing of different materials under the influence of dielectric oils. By systematically identifying potential incompatibilities, the right material choices can be made at the design phase.
Our methodology includes rigorous testing and analysis to assess how different materials could age when exposed to dielectric oils. This under a variation of degree of powertrain load, simulating various driving conditions. Failures revealed in this way can be prevented when they could otherwise have occurred during the life of the vehicle with an unsuitable fluid/material combination.
The result is twofold: a complete design guide for fluid-powertrain compatibility and a robust validation of an EVOGENTM e-fluid from Lubrizol.
-
Through the creation of comprehensive guidelines and datasets on material ageing, we developed a complete guide to systematically validate the compatibility of dielectric motor oils in EV drivelines. This will ensure that every powertrain component can withstand the chemical and thermal stresses caused by direct contact with dielectric oils. Early design flaws become a thing of the past.
- One of Lubrizol's EVOGENTM e-fluids, has been validated as compatible with various driveline components. It is a robust Single Oil that meets the stringent requirements for use in high-performance electric vehicles.
Verified Sealing Concept
To make this oil-jet cooling method suitable for high speed operations, we have developed a contactless hydrodynamic sealing concept to prevent oil from creeping into the air gap. The rotor acts as a small centrifugal air pump, keeping oil out of the air gap by creating a reverse air flow. This sealing concept has been industrially verified, read more about this in our blogpost.
This leads to an end to churning losses in the air gap, independent of the motor speed. The sealing concept can even further cool the motor by influencing the oil jet flow via the reverse airflow. The end result is a robust and efficient thermal design:
Future: Developing the optimal Single Oil architecture
Innovation in thermal management technology is an important building block for the next generation of electric vehicles. We are therefore continuing our ambition to develop the optimal thermal architecture through follow-up projects, such as the recently launched SmartSOS. An architecture with one multifunctional oil, tested and validated under realistic driving and (fast) charging conditions.
This is how we continue to shape the future of automotive technology: affordable, efficient, reliable and sustainable.
