Smoother gear operation with SPH fluid injection
- Alvaro Filho
- Aug 19
- 4 min read
Smoother lubrication with oil injection
Oil injection offers several advantages over traditional oil bath lubrication in gearboxes. This technique allows for a significant reduction in oil consumption, while providing greater precision compared to oil bath lubrication. The process enables precise control over lubricant supply, ensuring optimal lubrication at critical points. The localized application of oil helps minimize waste, resulting in lower overall consumption.
However, lubrication by injection requires a higher level of knowledge of the flow pattern and system dynamics. Moreover, it usually demands higher initial investment compared to oil bath systems. Therefore, detailed engineering insights in the early design phase of a gearbox are critical to realize optimum injector positioning and injection strategies.
A viable tool to cope with this challenge early in the design of a gearbox lubrication system is Smoothed-Particle Hydrodynamics (SPH).
Shifting gears with SPH fluid injection
Since version 2402, Simcenter STAR-CCM+ has incorporated SPH technology into an integrated CFD environment. In previous versions, the Smooth Particle Hydrodynamics (SPH) solver already allowed simulations of powertrain lubrication in oil bath configurations.
With version 2406, the functionality has been expanded to cover injection scenarios through the inclusion of specific inputs for SPH. This makes it possible to simulate oil injection with speed or mass flow imposition, as well as to define constant or time-varying distributions, such as in the lubrication system start-up process.
This makes it possible to visualize the behavior of the lubricant inside the gearbox with SPH and inlet boundary conditions. This helps to validate the direction of the oil in the gear elements, ensuring efficiency and reliability in lubrication.
Stay integrated with the power of Simcenter STAR-CCM+ as a platform
Thanks to the integration of SPH into our flagship Multiphysics platform, you can now harness Simcenter STAR-CCM+’s full suite of quantitative data analytics capabilities in conjunction with smoothed-particle hydrodynamics. For gearboxes, you can e.g. monitor churning losses by looking at the forces and torque evolutions throughout your simulation.
The torque report and graph do not depend on the surface mesh resolution. Even if you have a coarse representation of the surface mesh of your geometries, it will no longer affect the accuracy of the torque evolution. This ensures accurate results regardless of the details of the surface mesh.
More applications with rotating injectors
In the example above, you saw a static SPH fluid injection. Static inputs are commonly used when the flow entering the domain is not influenced by rotation. With Simcenter STAR-CCM+, it is also possible to set up a rotating boundary condition. In injection lubrication systems, rotary injectors are commonly used to supply oil lubricant to moving parts such as gears or bearings. The rotating inlet condition ensures that the lubricant flow enters the domain with the desired rotational movement. Proper modeling of this behavior is crucial for accurate simulations of powertrain lubrication performance.
This animation shows a simplified lubrication system in electronic machines. Using SPH for this application makes it easy to monitor where the lubricating oil goes with a simple workflow, compared to finite volume models.
Other applications are also possible thanks to the addition of inlet boundary conditions. You can start modeling water runoff or oil leakage applications in vehicles by observing where the liquid (water or oil) enters the vehicle. You can observe how the liquid spreads to different parts of the vehicle, where it accumulates, and how it interacts with other components.
To mesh or not to mesh
This question has remained relevant since the introduction of SPH: to mesh or not to mesh. As in previous versions, SPH offers distinct advantages for specific applications. Traditional CFD simulations often require CAD preparation and volumetric mesh generation, which can be time-consuming for systems such as gearboxes. SPH eliminates this step by operating directly with particles, providing a more fluid experience. The combination of intuitive workflows, CAD integration, and robustness in handling movements sets SPH apart in Simcenter STAR-CCM+.
In addition, an industrial gearbox can be simulated with SPH in about 12 minutes. Thus, for initial design screening, the SPH method is ideal for use with Design Manager for design exploration, quickly and easily eliminating low-performance designs. If your goal is to visualize the oil distribution inside the gearbox and monitor agitation losses, SPH is the best candidate for this application.
However, if air significantly affects the oil, or if you need to model spray inlets or observe heat transfer, or if you need to model mist (gas and liquid mixture) or model phase change or electromagnetism or other complex physics, it is recommended to use finite volume multiphase models, which are more suitable for greater accuracy.
The SPH and finite volume methods complement each other and always depend on the scope of your applications and the level of fidelity required to make the appropriate choice of model to use.
Surface tension modeling for SPH
The surface tension model was introduced with the aim of increasing accuracy in highly dynamic free flow simulations. This functionality allows the behavior of droplets and their interaction with surfaces to be represented. Contact angles can be defined for each solid contour, enabling simulations of hydrophilic or hydrophobic surfaces.
Ensure maximum efficiency in the lubrication of your gearboxes from the earliest stages of design! Schedule a meeting with CAEXPERTS and discover how to apply SPH in Simcenter STAR-CCM+ to accurately simulate oil injections, reduce losses, and accelerate engineering decisions with confidence.
WhatsApp: +55 (48) 98814-4798
E-mail: contato@caexperts.com.br
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