Time domain computational modeling of viscothermal acoustic propagation in catalytic converter substrates with porous walls

Abstract

Models for viscothermal effects in catalytic converter substrates are developed for time domain computational methods. The models are suitable for use in one-dimensional approaches for the prediction of exhaust system performance ͑engine tuning characteristics͒ and radiated sound levels. Starting with the "low reduced frequency" equations for viscothermal acoustic propagation in capillary tubes, time domain submodels are developed for the frequency-dependent wall friction, frequency-dependent wall heat transfer, and porous wall effects exhibited by catalytic converter substrates. Results from a time domain computational approach employing these submodels are compared to available analytical solutions for the low reduced frequency equations. The computational results are shown to agree well with the analytical solutions for capillary geometries representative of automotive catalytic converter substrates.

Computational performance of analytical methods for the acoustic modelling of automotive exhaust devices incorporating monoliths

“…As a result of increasing limitations on pollutant emissions, the use of after-treatment devices such as catalytic converters and diesel particulate filters has become a necessary practice in the design of the vehicle exhaust system. Although the design of these devices focuses mainly on the control of emissions (CO, NOx, HC and soot particles) [1], the acoustic aspects associated with catalysts and particulate filters also play a relevant role and have to be taken into account in the integral design of automotive exhaust systems from the point of view of noise control [2][3][4]. Therefore, not only noise attenuation due to silencers, but also the influence of catalytic converters and filters, should be considered in the development of analytical and numerical tools for predicting the acoustic behaviour of the complete exhaust system.…”

“…Therefore, not only noise attenuation due to silencers, but also the influence of catalytic converters and filters, should be considered in the development of analytical and numerical tools for predicting the acoustic behaviour of the complete exhaust system. For this reason, a number of publications can be found associated with the acoustic modelling of these devices [2][3][4][5][6][7][8][9].…”