EGRクーラ内へのPM堆積挙動に関する実験的研究

抄録

Exhaust Gas Recirculation (EGR) system with EGR coolers is one of the promising ways for NOx reduction in a diesel engine. Since PM and condensable hydrocarbons are contained in the exhaust gas of a diesel engine, they cause PM deposition on the wall in an EGR cooler. To improve performance of EGR cooler, the PM deposits in it should be reduced because the heat transfer performance is deteriorated by the PM deposition. In this study, effect of wall temperature on PM deposition in an experimental EGR cooler was investigated. The wall temperature of the EGR cooler could be controlled by the temperature of cooling water. The exhaust gas from a diesel engine was passed through the EGR cooler. The thickness of PM deposit was measured by a laser displacement sensor. As a result, the thickness of PM deposit increased with an increase of the exhaust gas passed through it, and the thickness did not so depend on the temperature of cooling water. The PM deposit layer in the upstream region of EGR cooler was thicker than that in the downstream region. It was found that PM deposit layers were separated from the wall in the case of lower cooling water temperature. The separation was probably caused by condensation of water in the exhaust gas.