Characteristics of scavenging flow in transfer ports of a motored two-stroke engine

Abstract

Abstract

A real two-stroke engine [specifically an Orbital Combustion Process X (OCP-X) engine] was optically modified for application of laser Doppler anemometry (LDA) and flow visualization. Two velocity components were measured in two transfer ports of the motored engine. Spatial and temporal distributions of velocity indicated that the scavenge flow was very complex, highly non-uniform across the transfer ports, and strongly time dependent with respect to the port opening and closing periods. Mean velocities averaged over these two periods characterize the scavenge flow in the transfer ports but do not represent the velocity peaks at the port opening and closing, respectively. Effects of the exhaust valve in the exhaust port and of depression applied to the exhaust port on the temporal distribution of scavenge flow in transfer ports were significant only for a high enough pressure difference between the crankcase and the exhaust.