In-Cylinder Flow Measurements in a Transparent Spark Ignition Engine

Flame development, combustion efficiency and emissions of a gasoline direct injection engine are strongly related with mixture preparation. Consequently, it is important to investigate the flow field and turbulence quantities at the parts of the thermodynamic cycle in which mixture preparation occurs. Flow field measurements were obtained by using 2D digital Particle Image Velocimetry technique in a 475cc optical single - cylinder Gasoline Direct Injection (GDI) spark ignition engine. The results include phase averaged velocity fields at 1000 and 1500 RPM with 100% and 25% throttle position. These sets of measurements were conducted for cold flow (motoring) conditions at three different planes including the tumble plane and the swirl plane. The flow was recorded at various crank angles between 340° and 20° before the combustion top dead center (BTDC) with an increment of 40°. The spatial averaged TKE (Turbulent Kinetic Energy) was calculated along with the TR (Tumble Ratio). It was observed that a tumble like motion with Counter Clock Wise rotation (CCW) was present near the maximum lift timing of the intake valves. The peak TKE at the intake stroke was present at -260° BTDC, with WOT (wide open throttle) and it was quite similar at 1000 and 1500 RPM. As expected, at 25% throttle position the TKE was less compared to the WOT case. The absolute value of TR, was much higher for the tumble plane comparing to the other measurement planes, both at 1000 and 1500RPM.