Abstract
In automobile exhaust systems, catalytic converters have become essential in reducing environmental pollutions. However, the main components of catalytic converters often produce large pressure drops in total exhaust systems, which both decrease engine power and increase fuel consumption. In addition to the need to reduce pressure loss, the flow passing through the catalytic substrate should be as uniform as possible, which provides a uniform thermal distribution and high catalytic-conversion efficiency. The goal of our research is both to reduce the pressure loss and to improve the flow uniformity under spatial constraints. In our past studies, we have proposed new types of devices and investigated their performances experimentally. Specifically speaking, we have revealed the possibilities of some types of flow deflectors with solid or shell structures, which are placed inside the diffuser part of the catalytic converter in order to suppress flow separation. These deflectors can reduce the pressure loss and improve the flow uniformity, simultaneously. However, such past studies concern only a steady flow. On the other hand, actual exhaust flows often involve large fluctuating components. So, in the present study, we attempt to show the influences of flow pulsation upon such flow-deflector performances as energy-loss reduction and velocity-profile improvement. As a result, the flow deflectors can be effective even for pulsating flows, as well as a steady flow.
Keywords: Exhaust system, Catalytic converter, Diffuser, Pressure loss, Pressure drop, Pulsating flow