Data Analysis in Unsteady Turbulent Flow Measurement: (Preliminary Study of Data Analysis of Turbulent Flow in Engine Cylinder)

The turbulence has a significant effect on the combustion process in an internal combustion engine. It is very important to separate the gas flow in the engine cylinder to the turbulence and the mean flow. The turbulence is defined as higher-frequency components in the turbulent flow. In this study, some methods of frequency filtering for distinguishing the turbulence components in the flow were investigated. The characteristics of four kinds of frequency filtering methods, that is to say, both digital and analog filters of Butterworth types, running-averaged and stationary time-averaged methods, were compared. These methods were applied to an unsteady jet similar to the flow in the engine cylinder, and the turbulence characteristics obtained were discussed.