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Numerical Simulation of Multi-Component Diffusion and Slip-Flow in Microporous MediaA method is presented, which enables the locally resolved calculation of multi-component gas transport in microporous media. The theoretical basis is formed by a fluid-dynamic model that comprises separate mass and momentum balances of each component in the gas mixture. By introducing component-specific slip boundary conditions, the model is made applicable to regimes of increased Knudsen numbers. After implementation into a commercial CFD-program the motion of a binary gas mixture in a virtual microporous structure is simulated. Analysis of the calculated velocity fields makes it possible to determine structural parameters that can be used in relevant 1D-models.

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Momentum, Heat and Mass Transfer in Exhaust Gas Sensors at Engine Operating ConditionsKnowledge of all relevant parameters affecting function and load is a precondition for optimal engineering of exhaust gas sensors. Access to those parameters by measurement is difficult and often impossible. Thus the development of a validated model to simulate operating behaviour of exhaust gas sensor was the aim of this work. Coupling of a 1D-engine simulation with a 3D-CFD simulation is done to predict convective momentum, heat and mass transfer to the sensor surface. Being results from coupled simulations, transient boundary conditions are applied to a further 1D-model to predict mass transfer inside the sensor. Signals of two exhaust gas sensors were simulated.