A Small-Scale Flow Rig for Swirl Studies of a Single-Valve, Reverse Uniflow 2S Engine

A small-scale flow rig has been constructed to investigate the swirl behavior of various intake manifold configurations. This effort is to support the development of a 10cc-size, single-valve reverse uniflow 2S engine. In this reverse uniflow geometry the incoming charge enters through a single valve in the engine head, and the burned gases are exhausted through symmetrically-arranged ports in the cylinder wall near bottom dead center. Port-directioning of the fresh charge, used in conventional (bottom-up) uniflow arrangements, is not available with this geometry, so another means to control the cylinder sweeping is sought. The flow rig has been constructed on a 2:1 scale, and three preliminary intake manifold configurations have been prototyped using a 3D printing machine. A straight manifold, a ramped tangential manifold and a basic helical design were manufactured. The rig has used charging pressures up to 0.75 bars above ambient where the swirl, flow and discharge coefficients can be characterized for various designs. PIV studies of the in-cylinder fluid dynamics, including recirculation regions near the valve, are also possible through the use of fused silica piping for the cylinder.