Alexander Trattner

Advantages and Challenges of Lean Operation of Two-Stroke Engines for Hand-Held Power Tools

Today, hand-held power tools facilitate specific jobs in many application areas, e.g. garden/landscape maintenance, construction industry and forestry. This market is highly diversified and demands special tools which are optimized for each application purpose (brush cutters, chain saws, etc.). Most of them are driven by two-stroke SI (spark ignition) engines equipped with a carburetor. High specific power, simplicity, low weight, low costs and compact design are characteristics of these two-stroke engine powered tools. The use of piston control or reed valves, oil-in-gasoline lubrication and loop scavenging is well established. Significant improvements regarding emission behavior have been achieved in recent years due to stratified scavenging systems which have become a standard. In order to respond to future challenges like continuing emissions and fuel consumption reduction the present engine technology has to be further developed. Several research areas are considered in order to improve the overall product, i.e. injection systems, ECU hardware and functionality, exhaust gas after-treatment and combustion systems [1, 3, 4, 5]. To date, the research on combustion systems for hand-held power tools tended to focus on rich mixture setting. The demands for high power and quick engine response are met by a rich mixture in part load and WOT (wide open throttle) operation. Moreover, the rich mixture reduces NOx formation and reduces thermal stress.

Energiewende und Wasserstoffwirtschaft

Die okonomischen, okologischen, sozialen und gesundheitlichen Folgen von Klimawandel und Umweltbelastung durch Schadstoffe stellen eine ernsthafte Bedrohung unserer Lebensqualitat dar. Eine nachhaltige Losung bieten Energiewende und Wasserstoffwirtschaft mit der kompletten Dekarbonisierung unseres Energiesystems durch den vollstandigen Ersatz der derzeit vorherrschenden fossilen Energietrager durch grunen Strom und grunen Wasserstoff, siehe Abb. 1.1.

Experimentelle Untersuchungen eines Ottomotors mit erweiterter Expansion über den Kurbeltrieb und die bedeutende Rolle der variablen Ventilsteuerung

Die Forderung nach einer fortwahrenden Senkung des Kraftstoffverbrauches heutiger Antriebe stellt fur die Automobilindustrie eine grose Herausforderung dar. Vor allem die Wirkungsgradsteigerung der Verbrennungskraftmaschine ist, neben effizienzsteigernden Masnahmen am gesamten Antriebsstrang, von besonderer Bedeutung. Ein vielversprechender Ansatz dafur ist die Realisierung eines im Verhaltnis zum Kompressionshub langeren Expansionshubes.

Analysis of working processes and efficiency assessment of hand-held power tools

Small displacement, single cylinder engines with spark ignition are used as a low cost propulsion in many applications like scooters, motor cycles, small boats and handheld power tools. These engines follow two- or four-stroke principle and are usually realized with a carburetor. They represent an affordable and simple as well as durable propulsion technology, but concurrently their efficiency is low and emissions are high. Consequently, the share of these small engine applications of total emissions and fuel consumption is not negligible. Therefore, the demand to increase efficiency of these engines is rising and the development of suitable and cost efficient methods is required.