Abstract
The Laser sheet particle track velocimetry procedure was improved by employing a two-color light source. Velocity vectors resolving the directional ambiguity could be obtained with high spatial resolution. The forward-scattering LDV adopting a high-power light source and large diameter / low density tracer particles revealed a potential for cycle-resolved turbulence analysis with high temporal resolution. Adopting these procedures, flow field in the pentroof combustion chamber of a two-intake-valve engine was analyzed. It was clarified that at the early and middle stages of the compression stroke, both tumble and swirl maintain distinctive vortex structures and at the late stage of the compression stroke, tumble and swirl are converted into many small eddies of relatively large scale. Experimental results demonstrated that because these eddies are distributed uniformly throughout the combustion chamber and the scale conversion proceeds, maintaining the equilibrium relationship, it is reasonable to treat these eddies as turbulence.
