Investigation of deviations in SI-engine behaviour due to manufacturing tolerances in cylinder heads

Abstract

Cast engine components are experiencing ever tighter tolerance requirements and at the same time a more complex cast design. The geometries, some of which are inaccessible, are tested for quality assurance on the basis of relevant component characteristics, among other things. The position check measures the actual position of a feature in a spatial dimension. Information about the alignment and geometry of the combustion chamber cannot be derived from the measurement methods applied. The use of three-dimensional measuring methods, e.g., imaging by computer tomography, can additionally record the spatial component position and the component geometry. Further measurement data can be derived from this, which serves to increase process reliability and component quality, and to increase component quality within an entire component batch. On the one hand, the cylinder head limits the working space by the roof of the combustion chamber, on the other hand, the cylinder head has a significant influence on the charge movement, especially at the beginning of the intake flow, due to the geometry of the intake ducts. On account the high demands of modern gasoline engines with tumble combustion process paired with Miller operation at partial load, variable timing, etc., mixture formation is important for efficient operation. Mixture formation in air- and wall-guided combustion processes depends on the components air duct and injection. From the point of view of cylinder head production, the mixture formation component air guiding is an elementary development approach for implementing efficient and sustainable component production while ensuring component properties. From this, the question can be derived as to what influence, for example, different dimensional tolerances in the combustion chamber size have on engine operation. To address this question, 3D simulations and physical test bench measurements were performed. With a variation of the above-mentioned intake duct and combustion chamber geometries and due to manufacturing tolerances, simulation results and measurement data were evaluated, analysed and presented in this paper. The influence of manufacturing-relevant tolerance deviations in the early process step of cylinder head production on combustion engine operation can be recognised in different ways.