Pressure-loss reduction and velocity-profile improvement in a catalytic converter by a flow deflector

In automobile exhaust systems, catalytic converters have become essential in reducing environmental pollution. However, the main components of catalytic converters produce large pressure drops in exhaust systems, which decrease engine power and increase fuel consumption. In addition to the need to reduce pressure loss, the flow passing through the catalytic substrate strate should be as uniform as possible, which provides a uniform thermal distribution and high catalytic conversion efficiency. The goal of the present study is simultaneously to reduce the pressure loss and to improve the flow distribution under spatial constraints. The authors herein propose new types of device and investigate their performances experimentally. Specifically, the possibilities of two types of flow deflector with a shell structure, which are placed inside the diffuser part of the catalytic converter in order to reduce flow separation, were investigated. In addition, using the particle image velocimetry technique and Pitot tube velocimetry, flow features such as the velocity profiles were elucidated. The tested converter has a standard cylindrical ceramic monolith substrate with channels of square cross-section. As a result, the two flow deflectors can reduce the pressure loss by 17 per cent and 22 per cent, compared with a no-deflector converter and can effectively improve the velocity profile.