A Study of Cycle-to-Cycle Variations and the Influence of Charge Motion Control on In-Cylinder Flow in an IC Engine

An experimental study is performed to investigate the cycle-to-cycle variations and the influence of charge motion control on in-cylinder flow measurement inside an internal combustion engine assembly. Molecular tagging velocimetry (MTV) is used to obtain the multiple point measurement of the instantaneous velocity field. MTV is a molecular counterpart of particle-based techniques, and it eliminates the use of seed particles. A two-component velocity field is obtained at various crank angle degrees for tumble and swirl measurement planes inside an optical engine assembly (1500 rpm and 2500 rpm engine speeds). Effects of charge motion control are studied considering different cases of: (i) charge motion control valve (CMCV) deactivated and (ii) CMCV activated. Both the measurement planes are used in each case to study the cycle-to-cycle variability inside an engine cylinder. Probability density functions of the normalized circulation are calculated from the instantaneous planar velocity to quantify the cycle-to-cycle variations of in-cylinder flows. In addition, the turbulent kinetic energy of flow is calculated and compared with the results of the probability density function. Different geometries of CMCV produce different effects on the in-cylinder flow field. It is found that the charge motion control used in this study has a profound effect on cycle-to-cycle variations during the intake and early compression; however, its influence reduces during the late compression. Therefore, it can be assumed that CMCV enhances the fuel-air mixing more than the flame speed.