Increasing the efficiency of internal combustion engines is of major interest for reduced greenhouse gas emission. A significant improvement potential is given with the reduction of friction losses. Here, especially the friction between the piston ring and the cylinder liner is of interest. This article describes a study with the target to enhance the piston ring–cylinder liner conformation through increasing the roundness of the deformed liner during the warm operation state. The approach is based on the assumption that a non-circular liner in the cold state can deform due to thermal and mechanical stresses toward a circular shape under typical hot operation conditions. To test this hypothesis, a computational model for a gasoline engine was built and simulated using advanced finite element methods. The simulation describes the deformation process of the liner from the thermal and mechanical stresses. First, the deformation of a circular liner is simulated, showing asymmetric deformations of up to 30 µm in the warm state for the cylinder positioned at the end of the four-cylinder bank. As experimental data are readily available, a comparison was possible, showing good agreement. Then, three liner configurations with non-circular shape in the cold stage are investigated. For an elliptically shaped configuration, a nearly circular-shaped liner is reached under typical operation conditions. This numerical approach shows the potential for reduced friction of the piston–liner arrangement within internal combustion engines. The planned next step is the extension of this method to three-dimensional shape aspects and the application to the geometry of our test engine of our lab where friction can be measured in detail with a floating-liner measurement system.

High pressure injection systems have essential roles in realizing highly controllable fuel injections in internal combustion engines. The primary atomization processes in the near field of the spray, and even inside the injector, determine the subsequent spray development with a considerable impact on the combustion and pollutant formation. Therefore, the processes should be understood as much as possible; for instance, to develop mathematical and numerical models. However, the experimental difficulties are extremely high, especially near the injector nozzle or inside the nozzle, due to the very small geometrical scales, the highly concentrated optical dense spray processes and the high speed and drastic transient nature of the spray. In this study, several unique and partly recently developed techniques are applied for detailed measurements on the flow inside the nozzle and the spray development very near the nozzle. As far as possible, the same three-hole injector for high pressure diesel injection is used to utilize and compare different measurement approaches. In a comprehensive section, the approach is taken to discuss the measurement results in comparison. It is possible to combine the observations within and outside the injector and to discuss the entire spray development processes for high pressure diesel sprays. This allows one to confirm theories and to provide detailed and, in parts, even quantitative data for the validation of numerical models.

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