Turbulence Measurements in a Direct Injection Diesel Engine by LDV

The airflow was measured by a LDV in a motored four-stroke direct injection diesel engine with a troidal cavity combustion chamber, under three different swirl intensity condition. The turbulence scale was calculated by a random sample data analysis utilizing multicycle velocity data. It has been clearly demonstrated that even though the swirl intensity was varied, the integral time scale increased once at the beginning of the compression stroke and decreased toward compression top dead center. On the other hand, the micro time scale hardly changed in suction and compression strokes. Furthermore, it has been revealed that the axial micro time scale was almost uniform in the cylinder under the high swirl condition, but the integral time scale remained large near the piston cavity center.