Simulation Research on the Effect of 2-Stroke Engine Exhaust Resonance on Aspiration

Exhaust resonance effect on the 2-stroke engine aspiration is investigated via one-dimensional simulation on GT-Power. Result shows that exhaust resonance is established when the number of oscillation periods per engine cycle derived from the engine speed and exhaust length is an integer. Exhaust resonance may raise or lower the trapping ratio, and the specific effect depends on the value of the number of oscillation periods per engine cycle. There is a liner regression relationship between the trapping ratio and average after back pressure. The primary way to improve the trapping ratio with the exhaust resonance is to increase the average after back pressure. The optimum exhaust resonance state is the one that suits the port timings so that the peak of exhaust pressure lies within the after charging period, raising the average after back pressure. For the case where the exhaust duration is 184°CA and the scavenge duration is 111°CA, the optimum number of oscillation periods per engine cycle is 3.