Low Emission Technologies for High-Performance Handheld Outdoor Products 2000-01-0896

This paper reviews the current and new engine technologies that are suitable to be implemented in light-weight outdoor power equipment that is mostly powered by two-stroke engines. It gives insight in the concerns associated with the improvement of known technologies and highlights trends for future engine developments. Among others, the paper covers ways for the conventional scavenging improvement, catalyst development, low pressure mixture injection, direct fuel injection, stratified scavenging and also four-stroke technology. These concepts are assessed with respect to performance, cost, size and weight.

Special emphasis is laid on the research and development of a catalyst concept for high-performance two-strokes and direct fuel injection. The catalyst is one of the easiest and most effective ways for emission reduction. However, measures have to be found to overcome the severe thermal difficulties. The paper presents ways how to achieve the emission goal of 54 g/hph (e. g. for the CARB-regulation) not for the detriment of performance and thermal stability. From the technical and the performance viewpoint, the direct fuel injection is a very attractive solution. Here, the aspects of port timing, injection timing and mixture formation are discussed. With direct fuel injection, a specific power in excess of 56 kW/l can be achieved at high costs while retaining the HC emissions below 40 g/kWh at rated speed.