Future Engine Technology in Hand-Held Power Tools 2012-32-0111

Today mankind is using highly sophisticated tools which contribute to maintain the standard of living. Nevertheless, these tools have to be further improved in the near future in order to protect health and environment as well as to ensure prosperity. Two-stroke engines equipped with a carburettor are the most used propulsion technology in hand-held power tools like chain saws and grass trimmers. The shortage of fossil resources and the necessary reduction of carbon dioxide emissions ask for improved engine efficiency. Concurrently, customers demand for an easy usage with high performance at all operating conditions, e.g. varying ambient temperature and pressure and different fuels. Moreover, world-wide emission limits will be even stricter in future.

The improvement of the emission level, fuel consumption and customer benefits, while keeping the present advantages of two-stroke engines, like high specific power and simplicity, are the goals of this research work. This paper describes the experimental results of several low-cost electrical mixture formation systems (low pressure direct injection, semi-direct injection and external mixture formation) in combination with a two-stroke engine. 3D-CFD simulations have supported the experimental investigations in order to gain insight into the complex interactions. Based on simulation and experimental results, the fundamentals of the different mixture formation processes are discussed. The results indicate potential for reducing emissions and fuel consumption while gaining additional benefits for the customer. With these improvements the two-stroke engine technology will likely be still the most used engine technology in hand-held power tools in the future although competitors like four-stroke and electrical engines show great technical advances in this small engine technology segment.