Flying PIV measurements in a 4-valve IC engine water analogue to characterize the near-wall flow evolution

摘要

For a deeper understanding of the highly unsteady near-wall boundary layer flows in internal combustion (IC) engines, PIV-based flow field measurements close to the inner cylinder and piston walls within transparent engines are required. The herein described flying PIV method in combination with a scanning light-sheet provides time-resolved PIV measurements in a transparent IC engine water analogue in a radial plane 1.5 mm apart from the planar piston crown while the piston is moving. The light-sheet is parallel to the piston surface and moves with the piston thanks to the scanning technique that synchronizes the sheet motion with the non-linear piston motion. A compact high speed camera is positioned within the piston shaft below the transparent piston head and records the particle fields within the illuminated plane in time-resolved manner. The measurements are realized in a water-analogue of a 4-valve engine at 950 rpm engine speed in real situation. Instantaneous pictures are compared to phase-averaged velocity maps and allowed to localize regions of high cycle-to-cycle fluctuations.