The high concentration of particulate matter (PM) in diesel
exhaust gas causes significant soot deposition on the wall of EGR
cooler, and reduces the heat transfer performance of the EGR cooler
and the reduction rate of NOx. The deposition of PM tends to be
occurred more severely with "heavy wet PM," which is more
frequently at the LTC (low temperature combustion) engine.
The objective of this work is to evaluate the effects of soluble
organic fraction (SOF) on deposit characteristics of the EGR
cooler. To measure reliable mean particle concentration values and
surrogate SOFs, the soot generator with SOF vaporizer was used.
As for two surrogate SOFs, n-dodecane and diesel lube oil,
deposit mass increased when they were injected. Especially from the
experiment results, it was found that the lube oil effect was more
significant than the n-dodecane effect and lube oil also had a
stronger effect on reduction of thermal conductivity by filling
pores in deposits. In detail, when diesel lube oil was injected,
the deposit mass per unit area increased 121% compared to dry soot
without injection at the coolant temperature of 40°C. In contrast,
effectiveness-drop after 10 hours increased just by 11%.