Development of a Low Emission Two-Stroke Engine with Low Pressure Fuel Injection 2006-32-0065

Based on the fundamental analysis of the two-stroke process and the first results of the 3D-CFD simulation (Paper No: SETC 2005-32-0098), the development of a small capacity two-stroke engine is the subject of this publication.

The developed 50 cm³ two-stroke engine is applied with a low pressure fuel injection system and allows, due to the special positioning of the fuel injector, two different scavenge modes. The first mode is a standard homogenous scavenge mode and the second one is for a stratified scavenged engine operation. Both modes can be achieved only by the adjustment of the injection timing without any restrictions concerning possible phasing. The system only deals with one fuel injector; special constraints concerning the transition between stratified and homogenous operation are not required. Any possible mixture can be applied between stratification and homogenous mode.

The development process will be described by design activities, 3D-CFD simulation results, research and development activities as well as the related test bench results of this engine. The modifications of the engine hardware, necessary for the application of the injection system to a two-stroke engine, are comparatively simple and are therefore an appropriate system to adapt up-to-date carbureted engines. The 3D-CFD simulation includes the simulation of the complete engine process starting at the reed valve including the crankcase, cylinder and also the entire exhaust system. The injection process with the spray adjustment is also a part of the 3D-CFD simulation process. The verification of the simulation results is accomplished by results of the engine test bench development and also by results of the optical visualization of the injection spray in fired engine mode. The benefit of this system on exhaust emissions is demonstrated by engine test bench as well as chassis dynamometer results. The achievable reduction of exhaust emissions is remarkable and the potential to fulfill future emission limits has already been demonstrated.