The cluster of excellence „Tailor-Made Fuels from Biomass“ at RWTH Aachen University develops and investigates new biofuel candidates, to reduce global emissions and create an alternative and sustainable diesel fuel. Biofuels pose a new challenge to existing common-rail injection pumps. Since fuels are used as lubricants for tribological contacts in these pumps, the deviating hydrodynamic properties in comparison to diesel can cause high leakage, wear, and a low overall-efficiency.

In order to ensure a reliable pump performance, especially for low-viscosity fuels or fuels with worse lubricity than diesel, an optimization of the tribological contacts is necessary. The most critical contact is the piston-cylinder contact. One possibility to reduce the leakage in this contact is the use of a hollow piston design. This design can reduce the gap between piston and cylinder by minor pressure-dependent elastic deformations of the piston.

In this paper, a first simulative look is taken at the compression behavior of the new piston design. The focus lies on the delayed pressure build-up due to the additional capacity caused by the shape of the piston. Based on the results, a new design approach is proposed subsequently in order to ensure a sufficient pressure build-up.

The manufactured contour of the new design is investigated in order to ensure the geometric properties and first measurement results are discussed. For the measurement, a low-viscosity fluid is used to compare leakage rates of the standard and the new hollow piston design. Based on the results, a conclusion is made, deriving further usage of the hollow piston.

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