Application of Multifiber Optics in Handheld Power Tools with High Speed Two-Stroke Gasoline Engines

When developing effective exhaust emission reduction measures, a better understanding of the complex working cycle in crankcase scavenged two-stroke gasoline engines. However, in a two-stroke gasoline engine detailed measurement and analysis of combustion data requires significantly more effort, when compared to a lower speed four-stroke engine. Particularly demanding are the requirements regarding the high speed (>10,000 rpm) which inevitably goes along with heavy vibrations and high temperatures of the air cooled cylinders. Another major challenge to the measuring equipment is the increased cleaning demand of the optical sensor surface due to the two-stroke gasoline mixture. In addition, the measuring equipment has to be adapted to the small size engines. Therefore, only a fiber optical approach can deliver insight into the cylinder for analyzing the combustion performance. The multifiber optics approach delivers extremely detailed results, whereas the cylinder-pressure indication as a purely integral number, cannot visualize the inflammation phase or reveal the origin of abnormal combustion events, e.g. self-ignition.