Multi-Dimensional, Transient Fluid Flow Simulations in the Manifold of a Four-Stroke Single-Cylinder Engine

Multi-dimensional computational fluid dynamics simulations were carried out on the intake manifold and cylinder of a four-stroke single cylinder two-wheeler engine. The complex geometry of the manifold and the engine cylinder, and the motion of the intake valve were taken into consideration. Both air flow and two-phase calculations were done to predict the trajectory of the liquid fuel and identify regions of impingement which could lead to film formation and high emissions at startup. The results show that the present geometry of the manifold is non-optimum as large recirculation zones are present. The two-phase simulations show that fuel transport is significantly affected due to the recirculation under idling conditions and significant impingement occurs. The numerical results obtained could be utilized to improve the flow in the manifold for lowering emissions.