Visualization of scavenging flow in the design of small two-stroke engines

An experimental test rig is presented, which enables visual examination of the internal flow of piston ported two-stroke cylinders. Similarity laws are applied to design the layout of the set-up. The reasons to use a liquid to represent the scavenging fluid are explained. Experiments are carried out which visualize the scavenging flow inside the cylinder. Colours play an important role in the visualization of flows. Careful selection of the dyes and the particular arrangement of different colours produce features of the three-dimensional and unsteady flow under investigation. The potential for future investigations to become an integrated part of the design process of small two-stroke engines is demonstrated.