Coupled 3D CFD model for the calculation of piston ring packages considering mixed friction, dynamics and structural deformations

针对提高机械元件效率和功率密度的需求，需要新颖、详细的三维仿真方法。因此，使用CFD（计算流体动力学）的流动模拟将继续在润滑摩擦系统的研究中变得越来越重要。在许多应用中，复杂的流固相互作用普遍存在，这对系统的行为有很大的影响。除了存在多流体相外，多体动力学、结构变形和混合摩擦条件是这些摩擦系统中常见的边界条件。因此，在本项目范围内，将开发将上述影响整合到CFD中的方法。作为内燃机活塞/气缸对的一部分的活塞环包是一个合适的应用实例。一方面，它提供了一个有趣和多样化的应用领域，因为内燃机将在未来继续发挥重要作用，通过进一步优化和使用新的合成燃料，活塞/缸对往往是发动机摩擦的最大比例。另一方面，它是一个复杂的系统，目前还没有CFD模型，这些模型在必要的细节深度上考虑了上述所有影响。新的计算方法包括开发活塞环包的三维CFD模型，并结合用户定义的函数，旨在改进对吹胀量和摩擦力的研究。特别重要的是活塞环的三维动态和变形，这是用有限元模型表示的。不仅要实现与流体力学解和实体接触的耦合，而且要开发有效的三维计算网格自适应算法。此外，还建立了混合摩擦模型以及考虑润滑油在缸套珩磨剖面中的存储的模型。最后，基于浮式尾管试验台的测量结果对模型进行了验证。在本研究项目的框架内，期望获得润滑机械元件中流体-结构相互作用的三维计算的普遍有效的方法能力。在项目结束时，除了关于活塞环包内摩擦和传输机制的全面细节外，还可以获得多相CFD与混合摩擦、结构动力学和用户定义网格动力学模型耦合的结果和3D部分模型，这些模型可以转移到其他润滑机器元件上。

Regarding the demand for increasing efficiency and power density of machine elements, novel, detailed 3D simulation methods are required. Thereby flow simulation using CFD (Computational Fluid Dynamics) will continue to gain in importance for the investigation of lubricated tribosystems. In many applications, complex fluid-structure interactions prevail, which significantly influence the systems behavior. Besides the existence of multiple fluid phases, multibody dynamics, structural deformations and mixed friction conditions are frequent boundary conditions in these tribological systems. Therefore within the scope of this project, methods for the integration of the mentioned influences into the CFD will be developed. A suitable application to exemplify this is the piston ring package as part of the piston/cylinder pairing of internal combustion engines. On the one hand, it offers an interesting and diverse field of application, since combustion engines will continue to play an important role in the future through further optimization and the use of new synthetic fuels, and the piston/cylinder pairing tends to be responsible for the largest proportion of the engine’s friction. On the other hand, it is a sophisticated system for which no CFD models exist yet, which take all the above-mentioned influences into account in the necessary depth of detail.The novel calculation approach, which is intended to improve the investigation of the amount of blowby and friction, consists of the development of a 3D CFD model of the piston ring package coupled with user-defined functions. Of particular importance are the three-dimensional dynamic and deformation of the piston ring, which is to be represented by a FE model. Not only the coupling with the fluid mechanical solution and the solid body contact must be implemented, but also efficient algorithms for the adaptation of the three-dimensional calculation meshes have to be developed. In addition, a mixed friction model as well as a model for considering lubricant storage in the honing profile of the cylinder liner are to be implemented. Finally, the overall model is validated based on the measurement results of a floating liner test rig. Within the framework of this research project, the acquisition of generally valid methodological competencies for the three-dimensional calculation of fluid-structure interactions in lubricated machine elements is to be expected. At the end of the project, in addition to comprehensive details on the friction and transport mechanisms within the piston ring package, findings and 3D partial models for coupling the multiphase CFD with models for mixed friction, structural dynamics and user defined mesh dynamics are available, which can be transferred to other lubricated machine elements.