Abstract
Exhaust gas recirculation (EGR) is an effective method for reduction of nitrogen oxide (NOx) in diesel exhaust. However, a kind of lacquers are deposited on the EGR valve or EGR cooler because of particulate matters and other components present in diesel exhaust, which are serious problems. In this study, to investigate the mechanism of the lacquer deposition, the components in diesel exhaust have been measured using a laser-ionization time-of-flight mass spectrometry (LI-TOFMS), which allows for real-time measurements of the volatile organic hydrocarbons (VOCs) and polycyclic aromatic hydrocarbons (PAHs). Temperature-dependent lacquers deposition was evaluated using a custom-built sample line, which had temperature slope between 323 K and 793 K, connected to the exhaust pipe of diesel engine. The components in diesel exhaust were measured where the lacquer was deposited in temperature range of 323-423 K. It was found that various kinds of VOCs and PAHs whose mass were approximately between 40 and 200 were detected and their emission trends had different from each other. It is considered that the species whose signal intensities decreased drastically in the temperature range where the lacquer was deposited probably contribute to the formation of the lacquer.
