Exhaust Gas Flow Behavior in a Two-Stroke Engine

The velocity variations of the burnt exhaust gas in a practical fired two-stroke engine operating under wide-open-throttle conditions were measured by a fiber LDV ( FLDV ). The characteristics of the exhaust flow are discussed in comparison with those in motoring and in a transfer port. The relation between velocity variation and pressure wave propagation in the exhaust pipe are also investigated. The measured results show that the velocity distribution in the exhaust pipe can be characterized as pulsative flow. The flow characteristics had large influence by the combustion pressure wave propagation. During exhaust and transfer-port opening, the intake flow and the blow-down flow have similar velocity gradient and peak location. The velocity distribution in the exhaust pipe was also measured, which showed pulsative flow variation having no recirculating vortex. The exhaust gas flow had very large velocity variation between EO and BDC which depended on the propagation of the sharp pressure wave generated by combustion. The main characteristics of velocity variation in the exhaust flow was similar to variation in the transfer-port flow during the period the transfer ports were open.