Fuel supply system to DOC by nanopore-ceramic tube and measurement of fuel evaporation rate

Abstract

When the deposited particles in DPF is oxidized, diesel fuel is injected to the diesel oxidation catalyst (DOC) for increasing the exhaust gas temperature. It is called a secondary fuel injection. However, it is difficult to form the uniform fuel mixture. If there is high fuel concentration region, hot spots and/or coking at the catalyst inlet face, leading to the potential damage of the catalyst. Also, the fuel must be completely evaporated to avoid the emission of harmful hydrocarbons in the outer atmosphere. Non-uniform fuel supply across the catalyst inlet face may cause incomplete fuel oxidation over the DOC. Thus, we may need an alternative approach for fuel supply system in the exhaust line. In this study, we have tested a fuel supply system to DOC using nanopore-ceramic tube. The fuel is uniformly vaporized on the surface of the tube filled with the diesel fuel, which automatically flows towards the DOC. Since we could not measure the vaporized gaseous component by an electrical low pressure impactor called ELPI+, the evaporation rate was evaluated in terms of the burning velocity of the premixed flame on a Bunsen burner. It was confirmed that most of water vaporized from the ceramic tube was gaseous water vapor. As the pore size of the tube was larger, the maximum evaporation rate increased. When the tube length or the tube outer diameter was larger, the fuel evaporation was enlarged due to the larger surface area of the fuel evaporation.