Compared to conventional oil bath lubrication, oil injection has a number of benefits for gearboxes. Compared to an oil bath, oil injection achieves better accuracy while allowing for a significant reduction in oil usage. In fact, the injection method allows for precise control over the distribution of oil, guaranteeing ideal lubrication at crucial points. When oil is injected exactly where it is needed, waste is reduced and total oil consumption is decreased. However, injection lubrication necessitates a deeper understanding of system dynamics and flow pattern. In addition, the initial expenditure required is typically larger than with oil bath systems.
Therefore, to achieve the best injector positioning and injection techniques, precise technical insights are essential throughout the early stages of a gearbox’s design. Smoothed-Particle Hydrodynamics is a useful tool to address this issue early in the gearbox lubrication system design process (SPH).
The “big entrance” of SPH technology into a single integrated CFD environment was Simcenter STAR-CCM+ 2402. The Smoothed-Particle Hydrodynamics (SPH) solver made it possible to target powertrain lubrication with oil bath applications in the earlier 2402 release.
In Simcenter STAR-CCM+ 2406, we interpreted the phrase “entrance of SPH” more literally: powertrain lubrication can now be addressed by injection thanks to the addition of SPH inlets. In particular, you can now force the mass flow or velocity of the oil to be injected. Furthermore, you can mimic a time evolution, like the lubrication system’s startup, or impose a continuous oil distribution. By combining SPH with inlet boundary conditions, Simcenter STAR-CCM+ 2406 now allows you to see the lubricant flow inside your gearbox. This makes it possible to confirm the exact orientation of the oil on gear parts, guaranteeing effective and trustworthy lubrication.
You may now use smoothed-particle hydrodynamics with Simcenter STAR-CCM+’s complete range of quantitative data analytics tools, all made possible by the inclusion of SPH into our flagship Multiphysics platform. For gearboxes, you may track churning losses, for example, by tracking the changes in torque and forces during the simulation. Having said that, the torque evolution is a further improvement for SPH in Simcenter STAR-CCM+ 2406. The surface mesh resolution is no longer a factor in the torque report or map. The accuracy of the torque evolution won’t be affected by your geometries’ coarse surface mesh representation any longer. This guarantees precise outcomes irrespective of the surface mesh details.
You observed a static SPH fluid injection in the scenario above. When rotation has no effect on the flow entering the domain, static inlets are frequently utilized. It is also possible to establish a revolving inlet boundary condition with Simcenter STAR-CCM+ 2406. Rotating injectors are frequently used in injection lubrication systems to supply oil lubricant to moving elements like gears and bearings. The lubricant flow enters the domain with the intended rotational velocity thanks to the rotating inlet condition. Efficient modeling of this behavior is essential for reliable powertrain lubrication performance simulations.
An e-machine lubrication system that has been simplified is demonstrated in this animation. Compared to finite-volume models, using SPH for this application makes it easy to track where the lubrication oil goes using a straightforward approach.
The addition of inlet boundary conditions in this updated version makes other applications accessible as well. You can begin modeling applications such as oil leaks or water runoff from vehicles by examining the locations where liquids (oil or water) enter and exit the vehicle. You can see how the liquid spreads out over the various areas of the car, where it gathers, and how it interacts with other parts. Although these applications are now possible, it should be mentioned that certain features—like the surface tension model we are developing right now—remain absent for better fidelity modeling.
Since SPH was first introduced, the central question has been: Should I mesh or should I not mesh? Regarding the prior release, SPH provides clear benefits for target applications in comparison to alternative multiphase models. For gearbox or E-machine applications, traditional CFD simulations frequently call for cleaning the CAD and building a volume mesh, which can be laborious and complicated. SPH completely omits this step. It works directly on particles dispersed across the computational domain, negating the need for a volume mesh. Customers gain from a more smooth encounter. SPH in Simcenter STAR-CCM+ combines strong motion handling, geometry flexibility, CAD integration, and user-friendly processes.
Moreover, SPH can replicate an industrial gearbox in roughly 12 minutes. Therefore, the SPH approach is perfect for early design screenings when combined with the Design Manager for design exploration in order to swiftly and easily reject low-performance design. SPH is your best option if your goal is to see how the oil is distributed inside the gearbox and keep an eye on the churning losses.
However, we advise using finite-volume multiphase models, which are better suited for the highest accuracy, if air has a significant impact on the oil, if you need to model spray inlets or examine heat transfer, if you need to model the mist (gas and liquid mix), or if you need to model phase change, electromagnetics, or other complex physics.
Finite volume and SPH approaches work well together, and the right model to utilize will always rely on the extent of your applications and the desired level of precision.
In conclusion, even though SPH technology has advanced significantly since its last release, achieving stable and precise inlet conditions is crucial to realizing all of its potential. Engineers can harness the power of SPH and investigate technical alternatives that convert complexity into a competitive advantage by carefully establishing these boundaries.
