Development of Dual Wall Air Gap Exhaust System

The strict new emission regulations have resulted in the development of new techniques to meet the control of cold-start emission in various competitive ways. In this study, the dual walled air gap exhaust pipe system is developed as an effective countermeasure to reduce pollutant exhaust gas emission, particularly to reduce pollutant exhaust gas emission at cold start and idling stage, in which the catalytic converter has not reached to light-off temperature. In this study, it is shown that dual walled air gap exhaust system can shorten the time to reach to light off temperature of the catalytic converter in cold start state, and reduce the emission of Hydrocarbon (HC) significantly due to its low thermal capacity and high thermal insulation effect. In the study, a thermal analysis of the dual walled air gap exhaust pipe system has been done using the computational fluid dynamics method. The analytical results were compared with the experiments obtained from specially designed bench tester, engine dynamometer tests. The analytical results have shown excellent conformity in both results. From the study the dual walled air gap exhaust system has been proved to meet the reduction in cold start emissions, particularly during the transient conditions and weight reduction target. Also it has been shown that an optimum gap size for dual wall exhaust system can be obtained from the results.