A Study on the Effects of Recirculated Exhaust Gas Upon NOx and Soot Emissions in Diesel Engines with Scrubber EGR System

The effects of recirculated exhaust gas on the characteristics of NO_x and soot emissions under a wide range of engine loads are experimentally investigated using a four-stroke, four-cylinder, indirect injection, water-cooled marine diesel engine operating at two engine speeds. The aim of this study is to develop the EGR control system for reducing NO_x and soot emissions simultaneously in diesel engines. The EGR system is used to reduce NO_x emissions. And a novel diesel soot-removal device with a cylinder-type scrubber for the experiment system is specially designed and manufactured to reduce soot contents in the recirculated exhaust gas to the intake system of the engine. It is found that NO_x emissions decrease markedly, especially at higher loads, while soot emissions increase owing to the drop of intake and exhaust oxygen concentrations, and the rise of equivalence ratio as the EGR rate is elevated.