A Study on the Factors Affecting the Uniformity of Urea and Exhaust Gas Using an SCR Simulator

Abstract

As it is difficult to confirm mixed shape and mixing ratio which depend on the actual mixer inside the SCR, the present study on mixed shape and mixing ratio has been conducted by producing an SCR system simulator. Total 19 sensors were installed and the system was designed not to allow formation of a negative pressure inside the exhaust pipe. The experiment was conducted setting engine rpm, temperature, mixer shape, and distance as the experiment variables. As a result of the experiment, in the case of non-mixer type, a phenomenon was found where urea became locally packed as the exhaust gas and urea were not mixed and, when an R-type mixer was applied, urea was formed being spread on the whole. It was also confirmed that uniformity index was increased by 8 % in average when an R-type mixer was used in comparison to that of the non-mixer type, and the non-mixer type failed to achieve flow uniformity of 90 % or higher while the case where an R-type mixer was used could achieve it when the distance was 20 cm or bigger. Based on such a result, changes in the uniformity of urea and exhaust gas depending on existence of a mixer, exhaust gas temperature, engine rpm, and distance could be confirmed. It is thought that additional studies are required to be conducted later on the effect of a change in the mixer shape on flow uniformity.