Abstract:

In order to predict the transmission loss of catalytic converters in automotive exhaust systems, efforts have been devoted recently to wave propagation through a capillary tube with a steady flow. Several theoretical models also exist. In this paper, general linearized governing equations are discussed and the characteristic features of each model are shown in conjunction with methods for solving the equations. Characteristics of the forward and backward propagating acoustic waves are investigated under the influence of steady flow and the dependency on the shear wave numbers is checked. Additionally, the presence of hydrodynamic wave components is examined under the steady flow condition. The application limits of the concurrent acoustic models are discussed as the shear wave number varies. Several prediction methods are applied to the calculation of the transmission loss of a stack of monoliths with and without mean flow considering the effects of radial components.