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Multidimensional model predictions and laser Doppler anemometer measurements are presented of the flow in a motored model engine equipped with a central shrouded valve. Although the accuracy of prediction, as assessed against the data, is at best moderate, the simulation is sufficiently close to provide valuable insight into the flow behaviour. an important finding in this regard is that the shrouded valve generates a long-lived tumbling vortex which is sustained and amplified by the compression process and in turn causes amplification of the turbulence, the TDC levels of which are more than twice those observed in similar studies with non-shrouded valves. It is concluded that inlet arrangements which produce such tumbling motions are likely to lead to enhanced flame propagation rates.

The results are reported of a combined experimental and computational study of steady flow through an axisymmetric valve/port assembly, the main objective of which was to assess the accuracy of the multidimensional model predictions of this flow. Measurements of the discharge coefficient, mean velocity and the turbulent Reynolds stress fields were obtained by hot-wire anemometry at various valve lifts. These were supplemented by flow visualisation studies. Predictions were made using a finite-volume method employing a body-fitted computational mesh and the k-ε turbulence model. Good agreement was found at low lifts, but at higher values this deteriorated due to the inability of the turbulence model to provoke the flow separations which occurred in the experiments. The conclusion is that for both idealised and practical ports multidimensional predictions will be of limited accuracy until better turbulence models become available.