Numerical Study on Clearance Flow in a Micro Internal Combustion Swing Engine

Numerical simulations on clearance flows between the swing arm and the engine body were completed by the Discrete Velocity Direction(DVD) model in a Micro Internal Combustion Swing Engine. The influences of the movement of the swing arm on the gas flow resistance and fluxes driven by the pressure difference within the gap were investigated and the effects of rarefication were discussed. The results show that when the swing arm moves in the same direction with the drop of pressure, the velocity slip caused by rarefication plays a leading role in the variation of gas flow resistance and fluxes. When the swing arm moves in the opposite direction with the drop of pressure, the recirculation flow and vortex occurred near the boundary and entrance respectively because of the enhancement of the wall effects.