Active flow control for maximizing performance of spark-ignited stratified charge engines

Cycle-to-cycle variation in stratified charge engines is a serious problem in the automotive industry. Due to cycle-to-cycle variation in engines, fuel injectors need to inject more fuel than necessary in order to have complete combustion in the engines. By reducing cycle-to-cycle variation, a better fuel economy could be achieved.The present study investigates the possibility of acoustically perturbing the intake flow at different frequencies and amplitudes to control the in-cylinder flow field. This research work concentrates mainly on an engine speed of 600 rpm and 270 crank angle degree (CAD), with the interest of changing the flow field in compression before ignition. Molecular Tagging Velocimetry (MTV) was used to measure the 2D-velocity field at the mid-plane of the engine cylinder.The experimental results showed that perturbing the flow acoustically has an effect in reducing the cycle-to-cycle variation. The level of cycle-to-cycle variation is measured based on U rms and V rms values. The free-run perturbation method and fixed-time perturbation method managed to reduce the U rms and V rms by about 30% in certain regions of the flow.