Abstract
The stringent exhaust emissions standards for SI engines (EU IV in Europe and SULEV in the U.S.) demand increasingly sophisticated exhaust-gas after-treatment strategies. These strategies now define the key technologies currently being developed by the automotive industry.
Desirable reductions in the light-off times of catalytic converters can be achieved by secondary-air injection promoting the exothermic oxidation of the HC and CO components of the exhaust gas. CFD analyses supporting the design of such a secondary-air injection system are presented.
An approach was taken, where the complexity of the simulations increased as the whole system became more and more defined in detail. In parallel with the development of such an approach a sophisticated verification program was also developed proving the quality of CFD results for compressible, highly pulsating flow in an exhaust manifold.
The analysis of various characteristic values and three-dimensional CFD results gave a physical insight into the phenomena observed and allowed the assessment of various designs.