A generalized renormalization group turbulence model and its application to a light-duty diesel engine operating in a low-temperature combustion regime

A generalized renormalization group closure model based on the “dimensionality” of the flow strain rate is proposed and applied to engine flows in this study. In the model, the model coefficients C1, C2, and C3 are constructed as functions of the flow strain rate. Computations were made for compressing/expanding flows in a diesel engine under motoring conditions. It was found that the generalized renormalization group model performs better than the standard renormalization group k−ε model in terms of its predictions of turbulent kinetic energy and model length scales. Computations in a diesel engine operating under low-temperature combustion conditions were also investigated to further assess the performance of the present model. Predictions of the spatial distributions of unburned hydrocarbons were significantly improved and agreed well with available experimental images. Engine-out unburned hydrocarbon emission was predicted to be smaller with the generalized renormalization group model than with the standard renormalization group k−ε model.

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