GPU-powered CFD Simulation Accelerates Lubrication System Optimization

Optimizing Gear Lubrication with CFD Simulation

Gearboxes, transmissions and other machinery with moving parts rely on lubrication to minimize resistance and wear. Poor lubrication can cause many different problems, including reduced energy efficiency, increased heat and shorter lifespan due to wear and damage. Gearbox designers and engineers need to ensure that contact points will receive sufficient lubrication, while mitigating turbulence effects in the oil such as churning and spray that waste energy.

There are many functional parameters for an engineer to consider, including the viscosity of the oil, the geometry of the casing, and active oil distribution systems such as oil jets. The flow of oil through the moving parts of the gearbox is a complex three-dimensional problem, and it is costly, time consuming, and nearly impossible to pinpoint problem areas with physical prototypes. Fast and accurate computational fluid dynamics (CFD) can be used to model and simulate the flow of oil between moving parts and reveal lubrication performance issues in real-world conditions.

SIMULIA XFlow provides robust CFD simulation technology that is well suited to solving lubrication problems. It simulates the multiphase flows and dynamic motion of gears using the Lattice Boltzmann Method (LBM). It has been validated with academic and industrial cases for high-fidelity results. SIMULIA XFlow offers 3D visualization of flows inside the structure, as well as standard KPIs for lubrication performance. It is also used to estimate the Heat Transfer Coefficient (HTC) on critical components for downstream thermal analysis on SIMULIA Abaqus, avoiding reliability issues.

Accelerate and Democratize Simulation with CFD Simulation

In order to accurately simulate lubrication performance, a high accuracy solver is needed, operating on a high-fidelity model of the system. This means that lubrication simulation has significant computational requirements. GPU computing allows complex gearbox lubrication simulations to be run quickly and efficiently, even on relatively modest hardware.

SIMULIA XFlow supports GPU acceleration using CUDA technology from NVIDIA. GPU-accelerated simulation speeds the performance of high-fidelity and intricate CFD simulations, and make them accessible to a wide audience, thereby democratizing access to advanced simulation capabilities.  For example, an NVIDIA L40 GPU can run a large complex gearbox simulation within one day.

Optimizing Designs Earlier in the Development Cycle

This acceleration powered by NVIDIA GPUs helps designers and engineers to take advantage of the collaboration capabilities of unified modeling and simulation (MODSIM) on the 3DEXPERIENCE platform. With the MODSIM approach, designers can use the simulation results immediately to explore the impact of design changes on the performance of their gearbox at the earliest stages of development. This helps reduce the risk of delays caused by test failures and expensive rework later in the development cycle. The rapid turnaround of CFD simulation with NVIDIA GPUs makes it feasible to use XFlow simulations to evaluate the performance of the design at any point in the development process.

In addition, GPU simulation means that it is more practical to generate multiple design exploration scenarios to sweep and automatically extract key engineering KPIs. Since each simulation run is accelerated, the entire design space can be explored faster and with greater resolution.

Case Study: Improving Automotive Gearbox Reliability and Sustainability

Automotive OEMs and suppliers need to ensure higher efficiency of gearboxes, in order to meet sustainability goals and to reduce vehicle energy consumption. They also need to ensure reliability to reduce the risk of failure and costly maintenance downtime. This is just as true of electric vehicles as it is of internal combustion engine vehicles. An oil jet lubrication system (OJLS) is a crucial technology for distributing lubricating oil optimally inside the gearbox, ensuring that all critical surfaces are lubricated without the need for large volumes of oil and the associated torque drag and churning losses.

In this case study, the XFlow GPU solver was used to assess the reliability of an automotive Electric Drive Unit (EDU) gearbox. This gearbox has been identified a susceptible to reliability issues, primarily stemming from the thermal failure of a key bearing connected to the input shaft from the motor. An OJLS has been engineered to tackle the root cause by ensuring precise lubrication and subsequent cooling of all bearings and gears.

From the simulation, we were able to extract Key Performance Indexes such as torque drag and individual component wetted area quickly. The simulation showed that the OJLS increased the oil coverage of the failure-prone bearing by over 3 times. In doing so, the OJLS mitigates the risk of thermal failure resulting from inadequate lubrication.

Although the OJLS introduced more oil into the system, carefully targeted oil jets meant there was only a 20% increase in torque drag associated with churning losses. This outcome proves that a well-designed OJLS far outperforms a mere augmentation of the initial oil volume within the system. Optimizing the OJLS without simulation would have been a much more challenging process, with considerable time spent building and testing prototypes – as well as the difficulty of extracting accurate KPIs from measurement data without considerable uncertainty. By running the simulations on GPUs, these results could be obtained much faster than a physical prototype would have provided.

Conclusion

Using SIMULIA XFlow for CFD analysis reveals the behavior of lubrication systems in gearboxes and powertrains without having to construct a physical prototype. By leveraging NVIDIA GPUs, XFlow can rapidly calculate KPIs such as churning losses and wetted area, allowing gearbox performance to be analyzed in less than a day. This acceleration enables designers and engineers to collaborate on using CFD simulation results throughout the development cycle to reduce time and cost of physical testing and accelerate the delivery of reliable gearboxes to their customers.

For more details watch the on-demand webinar GPU accelerated CFD for Powertrain Lubrication and Tank Sloshing Workflows | Dassault Systèmes®

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