TurbochargedTwo-Stroke SI Engine as Back-up Range Extender for Battery Electric Vehicles

Abstract

Installation studies indicates that a compact single-cylinder two stroke Spark Ignited (SI)-engine with a swept volume of 400-500 cc is small enough to install in the heavy-duty Battery Electric Vehicle (BEV) application considered here. Four-stroke engines of similar power to the two-stroke engine would need additional installation volume because of the larger cylinder heads, bulky oil pans and the need for more cylinders to create the same number of power-pulses per revolution. The power requirement for a heavy-duty back-up REX engine have been defined as 150 kW. A NA 400-500 cc single- cylinder two-stroke engine can deliver 60-70 kW, so a charging system is considered vital to reach the desired performance level.

This article demonstrates how a charging system can be developed to meet the specific needs for such an engine in a gas exchange point of view. The results indicate that the main issue for a charging system is to obtain a specific relationship between charge air and exhaust pressure to support the gas exchange process. An afterburner-assisted turbocharger system is proposed as the best option to reach the desired properties. The technology is applied to a 125cc single cylinder engine using engine experiments and 1D-simulations to demonstrate that a specific output of 440 kW/L have been obtained. which is what is needed for an upscaled engine to reach 150 kW. The engine is running on e85 and the afterburner system contributes to lower emissions as a trade-off for the concept.