Fundamentals of 'laminar' and 'turbulent' catalysis; 'turbulent' beats 'laminar'; Grundlagen der 'laminaren' und 'turbulenten' Katalyse; 'Turbulent' schlaegt 'Laminar'

Monolithic, laminar flow catalysts have been used in the automotive industry for the last 30 years for catalytic exhaust gas after-treatment of hydrocarbons, carbon monoxide and nitrogen oxides. However, even in the long time this technology has been used, only few studies were presented that describe the turbulent inlet and dominating laminar flow regimes in the catalytic converter. Presumably this is due to the fact that turbulent-like flows could not be technically realised. This was one of the reasons the development of catalytic converters became stagnant and improvements were only realized through higher cell densities, which reduced the diffusion path of the pollutants to the catalytically active wall. Diffusion is the molecular transport mechanism that is present in laminar flow. Laminar and turbulent flows have been modelled in such small channels. However it is complicated to model the non-linear heat and mass transfer under these conditions. Now that catalytic converters utilizing turbulent-like flows are technically producible and the catalytic coating can be applied, the next generation of ''turbulent'' catalytic converters will be developed using computational and experimental programs. These computational and experimental programs will illustrate the function of today's laminar flow catalytic converters and the effect of the new, more efficient ''turbulent'' catalyst converters. Results from engine tests have made apparent the cost saving potential of the new generation of catalytic converters. (orig.)