Abstract
EGR combustion system is one of the promising ways of NOx reduction in diesel engine. To ensure high volumetric efficiency of EGR, hot exhaust gas should be cooled down with EGR cooler. Since PM and condensable hydrocarbons are contained in exhaust gas of diesel engine, they cause exhaust gas deposits in EGR cooler. To improve performance of EGR cooler, exhaust gas deposits in it should be eliminated. This research focused on accumulation behavior of deposits in EGR cooler. The EGR cooler was placed on the exhaust gas line. An amount of deposits and their compositions were analyzed under various excess air ratios in engine operation, various exhaust gas temperatures at EGR cooler, and various exhaust gas flow rates. Mass of deposits was obtained from EGR cooler mass of before and after deposition test. Their compositions were analyzed with a particulate analyzer. It was found that deposit mass of EGR cooler increased with a decrease of excess air ratio, with a decrease of temperature of outlet gas of the EGR cooler, and with a decrease of exhaust gas flow rate. Further increase rate of deposits was not affected by the accumulated deposits in the EGR cooler, and most of EGR deposits was soot.
Keywords: Diesel engine, EGR cooler, Deposits, Deposit composition, HC, PM