Turbulence Measurements in a Direct Injection Diesel Engine Combustion Chamber by LDV

A new method named the modified correlation method with slotting (MCS) has been proposed to analyze the turbulence scale accurately from the random discrete data with non-uniform time intervals, usually obtained by LDV measurements. The reliability of the method was confirmed by the model data. By applying the method, the authors have analyzed the air flow and the turbulence in a combustion chamber of a motored diesel engine under the conditions of three different intensities of suction swirl and also around the fuel spray injected intermittently under atmospheric condition. The main feature of turbulence confirmed were as follows. The integral time scale increased once at the beginning of the compression stroke and then decreased toward the compression top dead center. The turbulence intensity near the intermittent fuel spray varied dependently on the variation of the mean velocity, and a high level of the turbulence intensity was observed near the periphery of the fuel spray in both the spray-axis component and the entrainment component. And the integral time scale increased significantly after the end of the fuel injection.