Three-dimensional modelling of aerodynamics and combustion in a spark-ignition engine

Numerical simulation and experiments were combined to gain a better understanding of phenomena occurring inside combustion chambers. A laser Schlieren method with fast motion pictures gives the position of the flame front in a transformed engine to give good optical access via a 'transparent' piston. The pressure measured simultaneously in the cylinder is used to determine the instantaneous energy release. The numerical analysis is based on the three-dimensional modelling of the intake, compression and combustion. Taking the movement of the valve into consideration, the intake is computed for a geometry very close to the one of the experimental engine. The two cases studied, corresponding to two different positions of a shroud on the valve, act as a support for comparing modelling and measuring. The first configuration creates a high-intensity swirl of the air. The second configuration produces a rotation movement of the fluid around an axis perpendicular to the cylinder axis. Study results are discussed.