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Design of experiments (DoE) has been used to optimise the accuracy of CFD predictions for diesel combustion and emissions simulations. Eight CFD simulation variables concerning grid geometry and simulation time step were used as the basis for a twenty-two point DoE analysis. The results showed that for practical CFD simulations the CFD predictions were heavily dependent on local grid distribution and the calculation timestep. From the DoE statistical models, two CFD setups were predicted to give optimal combustion and emissions results with CPU times of 11 and 44 hours, model (A) and model(B), respectively. These two CFD model setups were then used to assess the accuracy of CFD combustion and emissions predictions against a series of detailed measurements performed on a single cylinder engine fitted with a common rail fuel injection system.

An automatic hexahedral meshing technique has been combined with CFD to predict the steady flow through practical intake port/valve geometries. Two intake configurations were investigated. An asymmetric design consisting of one helical and one directed port and a symmetric design consisting of two directed ports. The automatic meshing technique dramatically reduces the mesh construction time to less than 15% of that achievable by the conventional route. Detailed LDA, laser sheet, and swirl measurements reveal that for certain flow conditions and port arrangements it is possible to obtain a good match between the measured and predicted in-cylinder flow structure. The best predictions of in-cylinder swirl were within 5% of the measured values. It is also shown that this approach to mesh generation is both economic and robust for practical engine designs, transforming CFD into a practical tool for the design of intake ports.