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One of the most significant current discussions worldwide is the anthropogenic climate change accompanying fossil fuel consumption. Sustainable development in all fields of combustion engines is required with the principal objective to enhance efficiency. This certainly concerns the field of hand-held power tools as well. Today, two-stroke SI engines equipped with a carburetor are the most widely used propulsion technology in hand-held power tools like chain saws and grass trimmers. To date, research tended to focus on two-stroke engines with rich mixture setting. In this paper the advantages and challenges of leaner and/or lean operation are discussed. Experimental investigations regarding the influence of equivalence ratio on emissions, fuel consumption and power have been performed. Accompanying 3D-CFD simulations support the experiments in order to gain insight into these complex processes. The investigations concentrate on two different mixture formation processes, i.e.

For the development of high-performance 2-stroke engines with internal mixture preparation it is essential to know about the interaction between charge motion and injection spray. With no prototypes available conceptual investigations can only render such information by using 3D CFD simulation. In this way an optimization of mixture preparation and charge motion can be achieved by varying the transfer and boost ports. To allow for the influence of these modifications on the mass balance (volumetric and trapping efficiency), the entire system of the loop-scavenged two-stroke engine has to be investigated. The state of the art calculation domain for 2-stroke 3D CFD simulation is bounded at the inlet of the crankcase (reed valve) and sometimes also at the outlet of the cylinders. The reasons lie in the so far not sufficiently reproducible components (e.g. reed valve) as well as in the reduction of calculation time.