Combustion Analysis with Residual Gas as a Design Parameter for Two-Stroke Engines 2018-32-0045
ABSTRACTIn a variety of applications two-stroke engines asserts their usage as a propulsion unit, for examples in off-road vehicles, scooters, hand-held power tools and others. The outstanding power to weight ratio is the key advantage for two-stroke engines Furthermore two-stroke engines convince with high durability and low maintenance demand. However, an increasing environmental awareness, the protection of health and the shortage of fossil resources are the driving factors to further enhance the internal combustion process of two stroke engines. The reduction of emissions and fuel consumption with a constant power level is focused.
Developments deal with the optimization of the combustion process itself or the enhancement of the exhaust gas aftertreatment. Especially in very small two-stroke engines an exhaust gas aftertreatment system is rarely applied, due to disadvantages regarding component temperatures and product costs. Beside different parameters, the exhaust gas back pressure mainly influences the residual gas content as well as the gas exchange in two stroke engines. Both are essential for the combustion process quality, which can be determined by values of 50% MFB, COV, glow ignition and knock behavior. Additionally, scavenging losses and the volumetric efficiency vary in dependency of exhaust gas back pressure. The emission level is significantly affected by these values. To gain deeper insights into these engine specific connections, a wide operation range concerning equivalence ratio (rich and lean) as well as ignition timing of a two-stroke engine is analyzed. The aim of research is to declare the limits of the combustion and gas exchange process. From this, possible optimizations can be derived.
Pascal Richard Piecha, Stephan Jandl, Stefan Sturm, Stephan Schmidt, Roland Kirchberger, Florian Schumann
Graz University of Technology, Andreas Stihl AG & Co KG
SAE/JSAE Small Engine Technology Conference