Exhaust Flow Separation in a Two Stroke Engine

The two stroke direct injected gasoline engine is in part characterized by low temperature exhaust flow, particularly at light loads, due to the fresh air scavenging of the combustion chamber during the exhaust process. This study investigated the possibility of separating the exhaust flow into two regimes: 1) high temperature flow of the combustion products, and 2) low temperature flow from the fresh air scavenging process. Separation of the exhaust flow was accomplished by a mechanical device placed in the exhaust stream. In this way, emissions from the exhaust could be handled by two different catalysts and/or processes, each optimized for different temperature ranges and flow compositions. The first portion of this study involved validation of a computer model, using experimental data from a single cylinder engine with a stationary exhaust port and splitter. The second portion of this study involved construction and evaluation of the hardware on both a flow bench and on a two stroke direct injected engine. A significant difference in the properties of the two separated flows was achieved. Significant temperature differences between the separated flows were observed, along with corresponding differences in other flow properties. Engine performance was not significantly affected. This hardware suggests a solution to the problem of emissions in low temperature exhaust flow of the two stroke direct injected engine.