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

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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.