ディーゼル機関用EGRクーラの伝熱特性におよぼす堆積物の影響(熱工学,内燃機関,動力など)  [in Japanese] Effect of Deposits on Heat Transfer Performance of EGR Cooler for Diesel Engine(Thermal Engineering)  [in Japanese]

Exhaust gas recirculation (EGR) is one of the promising systems of NO_x reduction in diesel combustion engine. In EGR system, hot exhaust gas is recirculated from the exhaust side of engine. To attain the high volumetric efficiency of EGR, hot exhaust gas should be cooled down with EGR cooler. Then EGR cooler with high cooling performance is required to ensure high NO_x, reduction. To improve the cooling performance of EGR cooler, exhaust gas deposits in it should be eliminated, because heat transfer performance is deteriorated with the deposits. In this study, light-off temperature of deposits was estimated in a test furnace as the first step of the experiment. It showed that deposits could be oxidized in an elevated temperature condition above 500℃. The total mass of deposits in an EGR cooler was estimated with gas analysis of O_2 and CO_2 in the furnace. The gas analysis showed that 80% of deposits mass was carbon. Further, heat transfer performance of the EGR cooler was evaluated and relationship between deposits layer thickness and overall heat transfer coefficient was discussed.