Technical Paper
Minimizing Short-Circuiting Losses in 2-S Engines by Throttling the Exhaust Pipe
1990-09-01
901665
An effective and simple method to improve the performance of a crankcase-scavenged two-stroke engine under off-design conditions is to reduce the fuel loss, due to short-circuiting, by controlling the pressure at the exhaust port. The present work presents a systematic study of the effect of throttling the exhaust pipe as a means of improving the torque, fuel consumption and emission in a two-stroke-cycle engine. The experimental observations were analyzed and extrapolated with the aid of a detailed computer program which simulates the engine cycle. It was concluded that: 1. The hydrocarbon emissions are significantly reduced when an exhaust contraction is applied. A reduction of 28% may be achieved at a wide range of engine speeds and loads, without a noticeable deterioration in die operation stability. 2. An optimum contraction ratio for HC emission has been observed and was found to be a complex function of the engine speed and load, but mainly dependent on the engine load. 3.
