Insights from an Instrumented Screw Press: Investigating pressure, torque, cage strain and flows dynamic

This study presents a comprehensive, real-time investigation of the mechanical and flow dynamics within screw press during oil extraction from sunflower kernels and non-dehulled rapeseed. Using an instrumented press equipped with high-frequency sensors for pressure, torque, and cage strain, the research reveals pronounced cyclic fluctuations in internal pressures and deformations of the cage, closely tied to screw rotation. These findings challenge the adequacy of conventional steady-state models and highlight the need for dynamic approaches to capture the true behaviour of oilseed matrices during pressing. Comparative analysis demonstrates that sunflower kernels, due to their higher deformability and filtration resistance, exhibit flatter pressure profiles and reduced energy consumption, but also limit maximum pressure and oil yield compared to rapeseed. Residence time distribution measurements further uncover complex material flow patterns, including significant backflow at higher screw speeds, necessitating hybrid modelling approaches. The observed correlation between cage deformation and torque variation suggests that structural rigidity is a key factor for optimizing press performance and energy efficiency. Overall, this work advances the mechanistic understanding of screw press operation and provides new insights for improving oilseed processing efficiency and equipment design.