Investigation of the intake tumble flow in a prototype GDI engine using a steady-state test rig 2001-24-0022

An experimental and numerical investigation, using the Laser Doppler Anemometry (LDA) technique and a 3D fluid-dynamic code (KIVA 3V), was carried out in a prototype engine under steady-state conditions. The aim of the present activity was the flow field characterization and the effect of the intake geometry on the in-cylinder tumble flow. A new steady flow test rig designed for capturing the tumble motion within a test cylinder, made by a blower and an engine head, was assembled to simulate the intake flow. The engine head was mounted on an aluminum cylinder, having the same bore as the real engine. The cylinder was provided with optical accesses on the periphery and a flat optical window located at the bottom to a depth equal to the stroke of the engine. The cylinder was also equipped with two cylindrical ducts, used as air outflow ports. LDA measurements were made, using two intake system configurations, on a vertical plane located at the cylinder axis and passing between the two intake valves. The instantaneous axial and horizontal components of the air velocity were acquired testing the two intake port geometries at the same valves lift and flow rate. The instantaneous velocities were processed by the time-averaging technique in order to estimate the mean velocity and the turbulence intensity. A standard version of the KIVA 3V code was used to evaluate the intake flow pattern within the cylinder. The substantial agreement between experiments and calculations suggests that, regarding air motion, an acceptable level of confidence may be assigned to calculations carrying on to design the combustion system of a DISI engine currently under development at Istituto Motori.