Flattening the Torque Curve of a Two-Stroke Engine with a Fluid Diode Installed at the Scavenge Port

The typical convex torque of a simple two-stroke engine having a port-controlled piston is attributed to the backflow through the scavenge ports. It is proposed here to suppress the backflow by installing scroll diodes at the scavenge ports. Experimental observations on a fired engine demonstrate the remarkable improvement achieved with the diodes installed. The effect of the diodes presence on the engine power and on the delivery ratio is discussed by using a recorded diagram of the crankcase pressure variation with crank-angle during the gas exchange process.