PM deposit layer formation and its broken away on a exhaust line surface of diesel engine

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EGR combustion is one of the promising ways for NOx reduction in a diesel engine. Since PM and condensable hydrocarbons are contained in the diesel exhaust, they cause PM deposition in an EGR cooler. To improve performance of EGR cooler, the PM deposits should be reduced because the heat transfer performance is deteriorated by the deposits layer. In this study, effects of wall temperature and exhaust gas inlet condition on PM deposition in an experimental EGR cooler were investigated.The thickness of PM deposit in the upstream region of EGR cooler was thicker than that in the downstream region. In addition, the thickness of PM deposit in low flow rate condition of the exhaust gas was thicker than that in high flow rate condition. Also, PM deposit layers were separated from the wall in the case of lower wall temperature. The separation was probably caused by condensation water in the exhaust gas.