Investigation of the Transient In-Cylinder Flow Inside a Two Stroke Engine with Particle-Image-Velocimetry

In order to meet future emission standards of small two-stroke engines (CARB 2), detailed knowledge of in-cylinder charge motion and mixture distribution is essential to be able to provide new ways of reducing exhaust emissions. The aim is to minimize fuel short circuiting accompanying the scavenging flow, which in turn leads to high HC emissions.

Therefore, an experimental investigation was carried out to investigate the in-cylinder flow structure during the gas exchange process inside a small two-stroke engine.

An optically accessible cylinder was fitted to a 64 cm³ two-stroke engine and the transient gas motion examined with Particle-Image-Velocimetry (PIV) under a variety of operating conditions and speeds up to 6000 rpm. The flow was investigated in two vertical cross- sectional planes through the cylinder and in a horizontal plane. The flow was observed through endoscopic optics to overcome the limitations associated with the design of an optical aperture in the small engine.