A Diesel Engine Emission System Based on Brownian Diffusion a Separation

Diesel engine exhaust poses an ongoing threat to human health as well as to the environment. Automotive exhaust treatment systems have been developed over the years to reduce the large amount of diesel particulate matter (DPM) released to the atmosphere. Current systems can be categorized as selective catalytic reduction, catalytic converters, and diesel particulate filters. This study presents an emission system that focuses on the removal of exhaust particles using Brownian diffusion of DPM toward fog drops followed by cyclonic separation of DPM rich fog drops. The experimental system consisted of a 13.2 kW diesel engine, heat exchanger to cool the exhaust to saturation temperature, ultrasonic fogger, cyclone separator, and recovery of waste particulate. Representative emission tests have been performed at five different diesel engine speeds and corresponding crankshaft loads. The scavenging coefficient as measured by the particle number concentration is 0.4-0.65 without fog and 0.6-0.85 with fog. These representative laboratory results demonstrated a 0.2-0.45 scavenging efficiency gain with the introduction of fog into the exhaust gas. Most of the collected diesel exhaust particles have a 0.5μm diameter. This emission reduction system has the potential to remove exhaust nanoparticles and can be scaled up for diesel engines with much higher displacements.