Investigation of particulate fouling in exhaust gas recirculation coolers in diesel engines

Emissions from diesel engines, such as nitrogen oxides (NOx), carbon monoxide and particulate matter (PM) impose a major threat to the environment and human health. As for the reduction of NOx emission though, the widely used technique is to return a portion of the exhaust gases to the intake of the engine after cooling them in a heat exchanger known as exhaust gas recirculation (EGR) cooler. However, EGR coolers are prone to severe fouling dominantly due to deposition of particulate matter, i.e. soot on heat transfer surfaces that result in profound deterioration of thermal efficiency. In this study, deposition and removal mechanisms of particulate matter are investigated. Also a one-dimensional model is developed which predicts the behavior of particulate fouling in EGR coolers taking into account the underlying deposition and removal mechanisms and energy equations associated with the particle mass conservation. The theoretical results are then compared with those of experiments of which the agreement between them shows the validity of the proposed model.