Best Available Technology for Emission Reduction of Small 4S-SI-Engines

Abstract

Small off-road 4-stroke SI-engines have extraordinarily high pollutant emissions. These must be curtailed to comply with the new Swiss clean air act LRV 98. The Swiss environmental protection agency (BUWAL) investigated the state of the technology. The aim was a cleaner agricultural walk behind mower with a 1 OkW 4-stroke SI-engine. Two engine designs were compared: side-valve and OHV. A commercially available 3-way catalytic converter system substantially curtailed emissions: In the ISO 8178 G test-cycle-average, HC was minimized to 8% and CO to 5% of raw emissions. At part load points, the residual emission was < 1 %. Simultaneously, fuel consumption improved 10%. Using a special gasoline (Swiss standard SN 181 163), the aromatic hydrocarbons were curtailed, e.g. Benzene< 1%, and fuel consumption further improved. Those results were confirmed in field tests. The engine is approved for retrofitting. Disquieting are the high emissions of u ltrafine particulates: the catalytic converter only minimizes the volatile but not the solid particulates.

Effect of the Volumetric Flow Rate Measurement Methodology of Positive Pressure Ventilators on the Parameters of the Drive Unit

“…On the other hand, the mean emissions of HC + NO x are equal to 2.4 ± 0.2 g/kWh, which means that they are lower than the permissible limits by 70%. The research is consistent with the results of other scientists who studied the engines of mobile non-road machines in real working conditions; e.g., Mayer et al, in 1999, showed CO emissions at a level of 180 g/kWh and HC + NO x at a level of 12.6 g/kWh [28]. Mitianiec and Rodak, in 2012, tested a 4.5 kW (two-stroke) engine, showing CO 2 emissions at a similar level of 100 g/kWh.…”